"Surface finishing - anodising, powder coating or wetcoating - is a process enhancing the properties ofaluminium in all its forms to give it a decorative visualappearance, to improve the metal's excellent corrosionresistance and to improve its wear resistance."

Aluminium Federation ofSouthern AfricaLight, Strong & Beautiful

A L U M I N I U M

AALLUUMMIINNIIUUMMSSUURRFFAACCEE FFIINNIISSHHIINNGG

UUSSEERR’’SS GGUUIIDDEE

INDEX

Introduction 3

ASFA 3

Surface Finishing defined 3

Types of Surface Finishing 4

Finishing Processes 5

Atmospheric Corrosion 6

Surface Finishes Comparison 8

Anodising 11

Powder Coating 15

Wet Coating 18

Care and Maintenance 19

Contact Details 20

References 20

Aluminium the MaterialAluminium is a remarkable material. It has a uniquecombination of properties that make it suitable for manydifferent applications in various alloy forms.

Aluminium is a light metal whose strength, corrosive anddecorating properties can be improved by alloying with variousother metals. It has good tensile strength over a wide range oftemperatures and has excellent corrosion resistance. Whenaluminium is exposed to air, a thin, glass-hard oxidised filmforms on the surface. This oxide film clings tenaciously to themetal's surface, presenting an effective barrier to the elements.Surface coating can make corrosion resistance even moreeffective.

Aluminium is an excellent conductor of heat and electricity. It ishighly reflective of light, heat, radiant energy and electric wavesand is non-magnetic. It is non-sparking, does not ignite or burnand is non-toxic. It can be formed by all known metal workingprocesses, is simple to fabricate and is suitable for joining,bonding and welding. It can be melted, cast, extruded, rolled,formed and machined. It is infinitely recyclable, an importantfeature in this age of energy and resource saving.

The Aluminium SubstrateFor a wide range of applications aluminium and its alloyshave the advantage that they are protected by the material’snatural hard and inert surface oxide layer that is formed inair and aerated water and that reforms instantly wheneverthe metal is cut or abraded. This oxide film inhibitscorrosion and consequently, in some uses such as industrialand agricultural roofing and cladding, aluminium is routinelysupplied in mill finish. Even windows have been suppliedin mill finish - the doors and casements in theJohannesburg Jeppe Street Post Office being a 70 yearold example, as is the Durban harbour Bayhead shed.

The demands of corrosion resistance, surface protectionand aesthetics have however relegated mill finish tothose situations where corrosion is slow and theproduct does not need to have a particularly attractivesurface finish. The surface finishes for aluminium that arecovered in this Guide fall into three main groups beinganodising, powder coating and wet coating.

Introduction

ASFA is an Association operatingunder the aegis of the AluminiumFederation of Southern Africa.

This is an AFSA publication and allcontents are copyright to theFederation.

Tel: (011) 453 3339Fax: (011) 453 3403

E-mail: afsa@afsa.org.zaWebsite: www.afsa.org.za

2

ASFA

The Aluminium Surface Finishers Association (ASFA) replacedthe original “Anoda” that was formed in 1992 as an Associationunder the aegis of the Aluminium Federation of Southern Africa(AFSA) - to address the needs of companies involved in thesurface finishing of aluminium.

The Purpose of the Association is to represent its membersin matters of common interest or concern in the fields ofaluminium surface finishing, relevant quality and environmentalmanagement and related research, technical advice andtechnology transfer.

In achieving its purpose, ASFA will, amongst other things:Provide a forum where members can discuss technicalmatters of common interest.Promote quality aluminium surface finishing that ASFA’smembers offer their customers, adhering to relevantSANS and other International Quality Standards.Promote the awareness of aluminium finishing and itsapplications through technical interchange and education.Promote the mutual benefit of membership to the surfacefinishing industry, including use of the ASFA hallmark / logo.Provide a customer focussed education / advice /information service including maintenance of relevanttechnical data.Facilitate training support and education for members andaluminium Stockists' staff.Make mandated representations on behalf of membersand the Industry on relevant matters opposite regulatorybodies.

ASFA thrives on the participation of its members. TheAssociation, through its members and the Federation,incorporates the best knowledge pool in aluminium surfacefinishing in Southern Africa. Over the years, this knowledge hasbeen accessed to produce a definitive guide on aluminiumsurface finishing in South Africa, namely the "Aluminium SurfaceFinishing User’s Guide". This publication contains technical andpractical guidelines and has proven successful with architects,specifiers and other users of surface finished aluminium.

Industry stakeholders include companies engaged in aluminiumfinishing, suppliers of products and services to the finishingcompanies, purchasers of coated products and specifiers ofsurface finishes.

Introduction

What is Surface Finishing?With the wide selection of goods available to consumers, firstimpressions are extremely important. Often, the value andsuccess of the product is based on immediate judgements - anda critical factor in this regard is the article's appearance orpackaging.

Aluminium provides an ideal base for further finishing of goodsin the form of a decorative coating. The size and range ofsurface finished products is vast - including goods in thepackaging, mechanical engineering, transport, automotive,electrical, pharmaceutical, architectural, building, domestic and'white' goods markets. Colour addition is used for decorative,instructive and protective uses.

All coatings may look similar at first glance, but there are manyfactors that will influence the lifespan of a good or bad surfacefinish over time. Surface quality is directly dependent onsurface treatment, film thickness, process control and provedspecified standards.

Regarded for too long simply as a means of corrosion protection,surface treatments in fact modify the condition or properties ofthe surface of the metal in a variety of ways:

They modify certain properties of the metal surface suchas surface hardness and abrasion resistance.They alter its appearance.They contribute to the decoration of the metal.They assist the adhesion of coatings such as paint, varnishand bonding adhesives.They provide further protection from corrosion whileimparting a durable appearance to the product.

Price is only a single aspect of finishing as the total cost must betaken into account. Developers, contractors, specifiers andother users of coated aluminium products are well-advised totake all the necessary measures to ensure that proven qualityassurance practices are maintained, thus ensuring that anygiven project will have the best aluminium finish available.

The most common types of surface treatment for aluminiumalloys are:

DegreasingMechanical surface treatmentChemical surface treatmentChemical conversionChemical brighteningAnodising (anodic oxide)Powder coatingWet coating

3

TABLE 1: Types of Surface Treatment

Type Technique Characteristics

Extruded Fine lines on extruded surface Decoration, Guidelines to future positioning, Fine lines cover small imperfections.

Mechanical Grinding / brushing

Polish and buffing

Vibration polishing

High finish polishing

Shot / grit blasting

Fine lines in the direction of grinding. Gives a silk or matt appearance.Produces a flat even surface.

The grinding lines partly disappear with polishing. Reduces “stress risers”.Removes die lines and tool marks and surface blemishes.

Yields a matt to shiny surface suited to small batches and mass produced parts.

Mirror finish, usually followed by bright anodising.

For cast aluminium components to remove cast skin and improve appearance.

Chemical Milling

Etching

Brightening (prior to anodising)

Chromating / phosphating

Electrochemically plating withcopper, tin, nickel or silver

Removes surface to desired depth. Can be used for signwriting.

Pretreatment to various finishing processes. Leaves a matt or silky appearance. Different etchants leave slightly different textures that may show up inanodising sheen.

Removes surface texture and gives a mirror finish. Film usually < 15 microns

Pretreatment prior to powder or other coating systems.

Improves corrosion resistance / gives good soldering surface /conductivity and reflectivity.

Electrochemical Decorative anodising

Hard anodising

Electrolytic polishing

Gives a hard, natural or coloured oxide layer up to 25 microns.Mainly for decoration - resists pitting corrosion but also adds wear resistanceand electrical insulation.

Gives a grey to brown coloured hard oxide layer of 75 - 125 microns.Mainly used for engineering purposes to resist abrasion / wear.

Gives a smooth surface with high reflectivity.

Organic surfacecoating

Powder coating

Screen printing

Coating with protective foils

Wet coating

Gives various degrees of protective and decorative finishes that can withstandheavy chemical attack (provided surface coating is unbroken).

Printing of text, décor patterns, etc.

For decoration, protection or other properties.

Mainly used in capital intensive operations for coil coating, effective andefficient. Mainly for building industry.

Types of Surface Finishing

4

Type of Finish to be SpecifiedThere are a number of factors to consider when specifyingsurface finishes. Different finishing processes may be specifieddepending on the use or application of the final product. Someof the factors to be considered are:

Appearance: bright, matt, coloured, brushed, otherEnvironment of use:

Interior (architectural, commercial, decorative, other)Exterior (architectural, marine)Industrial / Automotive (corrosive or non-corrosiveapplication, resistance to wear or abrasion, other)Underground (mining, cabling, piping)Aerospace (corrosive resistance, dielectric, emissivity,fatigue strength, other)

Criteria for Specifying FinishThe performance of surface treatments depends directly on thequality of the surface preparation. Anodising and powdercoating are complex processes that are constantly beingimproved. Specifiers should insist on adherence to SANS orInternational Standards to ensure that the surface finishperforms in the expected manner.

When specifying surface finishes for aluminium products, thefollowing specific criteria should be addressed:

Alloy and temper of aluminium to be usedThe alloy and temper of the product to be anodised will affectboth the strength and appearance of the part after it is treated.Various combinations of constituent elements cause eachaluminium alloy to react differently in the coating process; thisis particularly evident between alloy series. As a result, eachalloy or alloy series yields a different appearance, even iftreated to identical coating processes.

Mechanical finish, if any is requiredIf specified, mechanical finishing is done before chemicalfinishing or andodising. Mechanical finishes give surface textureor remove surface defects and irregularities. Appearance canbe varied but usually gives a uniform, matt finish, directional ornon directional-sanded finish, or a specular (mirror-like) finish.The mechanical finish shows through the anodic oxides becauseuncoloured anodic oxides are transparent or translucent andanodic oxides conform to the surface texture. Examples ofmechanical finishes are buffing, polishing, sanding, sand blastingand shot peening.

Grinding requires a rotary grinder with a bonded adhesive cupwheel or canvas wheel faced with suitable abrasives. Low speedgrinding (1500mm/min) using aluminium oxide is preferred toavoid overheating the surface.

Machine polishing requires wheels or belts that have abrasiveseither bonded to them or sprayed onto the wheel at regularintervals. Both contact and mush polishing methods are used,the latter being more common. Polishing can include a buffingoperation to remove emery marks.

Chemical finish in preparation for anodisingChemical treatment of an item significantly affects itsmattness or brightness (specularity). Chemical treatment isdone prior to anodising and is a very important factor in thefinal appearance of the anodised part. The pre-anodisechemical treatment of aluminium is often called the cleaning,clean-up or pre-treatment phase of the process.

Electro and chemical polishing approaches are used to smooththe metal surface through relative attack on the outstandingsurfaces where the surface to volume ratio is higher. As a result,a bright finish is achieved and a typical application would behollow ware.

Acid and alkaline etching is commonly used for lithographicplates, electrolytic capacitors and nameplates to mention but afew. Etching requires a chemical reagent to attack and roughenexposed surfaces of the metal to a suitable depth. In practice,the surface not to be etched is covered with a coating such aswax, that does not react with the reagent. The areas to beattacked are then exposed or exposed in order if differentdegrees of attack are required. Both alkaline and acid etchantscan be used. The former are more common as they arecheaper and easier to handle.

Anodic oxide requirementsThe anodic finish is the result of carefully controlled electro-chemical oxidation of the aluminium surface. There arevarious types of anodic finishes. Each finish is specified to obtaincertain appearance and/or performance characteristics desiredaccording to the end use of the product.Some of the characteristics of anodised surfaces are:

DecorativeAbrasion resistanceReflectiveDielectric, insulatingCorrosion resistanceColourAbsorption / emissivity of heat

Finishing Processes

5

Aluminium and AtmosphericCorrosionAluminium enjoys the advantage of a hard, inert oxide film thatforms instantaneously when the metal is cut or abraded. Thisoxide film inhibits corrosion and as a result, in some uses suchas industrial and agricultural roofing and cladding, aluminium isroutinely supplied in mill finish. Even windows, doors andcasements can be supplied in mill finish.

The demands of corrosion resistance, surface protectionand aesthetics have however relegated mill finish to thosesituations where corrosion is slow and the product doesnot have to be finished in a specific brand colour or wheredulling and roughening of the surface is not important.

The Concept of CorrosivityThe corrosivity of an atmosphere can be defined as the abilityof the atmosphere to cause corrosion in a given metal or alloy.ISO 9223 specifies the key factors in the atmospheric corrosionof metals and alloys and defines categories of corrosivity onthe basis of the constituents of the atmosphere, and inparticular the levels of chloride and sulphur dioxide present,in combination with the time-of-wetness of metal surfaces.

ISO 9223 also allows the classification of corrosivity to be doneusing corrosion rate measurements of standard specimens ofcommon metals and provides a table relating the corrosivitycategory to these corrosion rates for the first year of exposure.

While the category can be determined from a one-yearexposure of a suitable coupon, the corrosivity category thusderived can in turn be used to estimate the long-termeffects on metals: given the category, the average corrosionrate over the first 10 years of exposure can be found inISO 9224 [4]. This can be useful in estimating, forexample, whether an unpainted galvanized coatingover steel is a viable protection, or whether mill-finishaluminium will achieve a particular service lifetime.

Conversely, if 10-year or equivalent data are availablefrom long-term exposure and analysis of metal samples,then these may be used to determine the associatedcorrosivity categories.

TABLE 2: The Corrosivity Categories(as applied in Table 4, page 7)

Category Description

C1 very low

C2 low

C3 medium

C4 high

C5 very high

TABLE 3: Atmospheric Corrosion in South AfricaComparing performance of Aluminium vs Galvanised Steel sheeting

Description Type of corrosion Mild steel* corrosionrate µm/yr

Galvanised steelsheet** life in years^

Aluminium sheetlife in years

Intertidal to 5kminland

Severe marine 100 - 300 Up to 3 15

Desert marine (mists) Severe marine 80 - 100 0.5 - 2 15

Temperate marine Marine 30 - 50 3 - 7 20

Sub-tropical marine Medium to severe marine 50 - 80 3 - 5 >20

Desert inland dry Desert <5 > 30 >30

Inland Rural 10 - 20 > 20 >30

Inland urban Inland industrial ++ 15 - 40 5 - 15 20

Urban coastal Marine industrial ++ 50 - 150 1 - 3 20

Inland arid Semi desert 5 - 10 > 30 >30

KEY:* Higher corrosion rate usually indicates proximity of sea.** Commercial grade Z 275g/m² (unpainted).^ Life in years - until 5% of surface area showing red rust.

++ Industrial implies pollution present in atmosphere.Temperate marine & Sub-tropical marine usually from 5km inlandup to first mountain range.

Atmospheric Corrosion

6

TABLE 4: Corrosivity areas derived for Southern Africa with associatedISO corrosivity ratings

Code Geographic Area Distance from Ocean Description ISOCategory

Comments

A Namibia and NW Capeshore-line

To 5 km Desert shore-line andcoastal fog zone

Above C5 N. of Olifants River

B W. Cape Atlanticshore-line

To 3 km Arid shore-line with fog orstrong winds

Above C5 False Bay to Olifants River

C W. Cape coastal To 5-15 km Coastal area C4 To range of fall-out ofsalt aerosols

D W. Cape urban To 25 km Coastal urban/industrial C5 Cape Town andsurrounds

E S. and E. Capeshore-line

To 1 km Temperate shore-line C5 Distance from ocean varieswith terrain

F S. and E. Cape andNatal south coastal

To 5-10 km Temperate coastal C4 Distance from ocean varieswith terrain

G KZN shore-line To 4 km Subtropical shore-line Above C5 KZN to Maputo

H KZN coastal To 15-25 km Sub-tropical coastal C4

I Durban urban To 10 km Urban and industrial, inlandof shore-line

Upper C5 Amanzimtoti to DurbanNorth

J Richards Bay To 15 km Urban and industrial, inlandof shore-line

Lower C5

K Coastal cities To 10-15 km Industrial and heavytraffic areas

Lower C5 Areas of Port Elizabeth,East London, Pinetown

L Highveld general area - Rural and suburban areas C3

M Highveld urban andindustrial

- High-traffic urban, or closeto heavyindustry

C4 East Rand, areas ofPretoria, Witbank

Remainder of the region: C2 to lower C3 depending on climate.

Atmospheric Corrosion

7

NOTE:Metal corrosion dependson time of exposure tomoisture and relativehumidity and temperature.Rate of corrosion reducesrapidly the greater thedistance from the sea.For aluminium, aggravatingconditions can be a strongsulphurous atmosphere, theoccurrance of chloride saltsand stagnant water - but theright aluminium alloy stilloutperforms copper, zincand carbon steel! Regularcleaning and surface coatingsreduce the affect onaluminium.Pitting corrosion inaluminium may be unsightly,but it is not structurallysignificant.

Corrosion ResistanceMany decades of experience with applications in a variety ofmarkets including construction, land-based installations andshipbuilding have shown that aluminium and its alloys in the1000, 3000, 5000, 6000 and 8000 series have excellentresistance to atmosheric corrosion and to marine, urban andindustrial environments.

Combined with its light weight, aluminium’s excellentcorrosion resistance accounts for the growth of aluminiumapplications and offers users a number of advantages:

aluminium equipment can have a very long service life. It isnot uncommon to find roofing, wall cladding panels,marina installations and boats with decades of servicebehind them. This is also true in the field of transport andmany other applications,aluminium maintenance is minimal even when no extraprotection (painting, anodising) is provided. When aluminiumis painted, repairs are fewer and less urgent because theparent metal generally resists corrosion very well.Aluminium alloy products do not entirely eliminate theneed for maintenance, especially in buildings. It is wellknown that surfaces that are not cleaned are moresensitive than others, and that a surface build-up canaggravate corrosion (this is true of all metals and alloys).aluminium’s corrosion resistance maintains the appearanceof the equipment made from it. This is a useful salesargument, especially in industries where users want tokeep their products looking good for less cost.Commercial vehicles, outdoor municipal amenities andtraffic signs (indicator boards, gantries) are good examplesof this.

Finally, the process of anodising to a depth of a few microns canhelp create and preserve visual properties (high-qualityreflectance for retro-reflectors) or decorative features (luxurypackaging for cosmetics, decorative paneling for buildings).

Aluminium’s resistance to corrosion comes from the oxidesurface which is impermeable and integral with the base metal,staying stable for pH values between 4 and 9. The mostfrequent types of corrosion are galvanic, pitting and crevicecorrosion. Galvanic corrosion can be easily prevented byinserting an insulating material between the two differentmetals or by cathodic protection. Pitting can be prevented bysurface coating and crevice corrosion by judicious design.

Atmospheric Corrosion

8

Location Distancefrom sea orsourceof corrosionagents (km)

Exterior use -Recommendedmicrometres(µm)

Interior use -Recommendedmicrometres(µm)

WesternCape(West ofHermanus)“C”

<22 - 25>25

252515

251515

SouthernandEasternCape“E, K”

<22 - 20>20

252515

251515

NatalSouthCoast(south ofAmanzimtoti)“F”

<22 - 15>15

252515

251515

Durbanarea andNatalNorthCoast“G, H, I, J”

<22 - 25>25

252515

251515

Near achemicalor relatedprocessplant“M”

<5>5

2515

2515

In areaswherewindborne sand maybe abrasive(WesternCape Coastand theKarooaroundBeaufortWest)

Notrelevant

25 15

Otherareas

Inland 15 15

Table 5: Recommended Specificationof Anodised Coating Thickness(Please refer to the map on page 7)

Selection of Powder Coating Material

Location Exterior useRecommendedmicrometers (µm)

Interior useRecommendedmicrometres (µm)

All areas Polyester powderto SANS 1578.60-80µm metal coating inaccordance with SANS 1796or other internationalstandard.

Epoxy or Epoxypolyester powderto SANS 1274.50-80µm

TABLE 6: Finishing Comparisons

Parameter Anodising Powder Coating Wet Coatings

Specifications(ensure relevant use of mostcurrent revision)

SANS 999, 1407 and 10322apply. Also Qualanod.BS EN 755 applies to surfacecharacteristics of extrusions.

SANS 1578, SANS 1274,SANS 1796 and SANS 10322apply. Also Qualicoat.BS EN 755 applies to surfacecharacteristics of extrusions.

ASTM D3663 for PVDFfluorocarbon. AAMA 605.2.92for baked organic coating.

Colour range Extensive range but notall are suitable for exterioruse. Inorganic and organicdyes used. SANS 1091applies.

Full range available foreither interior or exterioruse. Critical to specifythe type of powder to beused.

Dependent on type ofcoating used, a large rangeis available. PDVF colours arelimited

Appearance Anodising gives a crisp, clean,metallic appearance - innatural or colour finish

Powder coated aluminium maylose that crisp appearance dueto the flow of the powderduring curing.

Colour fastness Exterior anodising hasexcellent light fastnessproperties, if correctlyprocessed.

Colour fastness is dependenton the type of powder used.Important to specify thecorrect product.

Coating thicknesses 5 - 25 microns depending onapplication.

60 to 80 microns 20 to 28 microns

Life expectancy Warranted 10 years.Experience over 20 years.

15 - 20 years if applied inaccordance with powdermanufacturer’s conditions.

Warranted 10 years.Experience over 25 years.

Installation Anodising is prone to attackby wet mortar and certainacid attacks.

Powder coating is less proneto attack by mortar, but isalso prone to certain acidattack.

Long lasting mortar resistance

Abrasion resistance Hard surface, long lastingabrasion resistance.

Not abrasion resistant, butlong lasting.

Inert coating with goodchemical resistance andseawater attack.

Maintenance Wash down with a neutraldetergent every 3 to 6months.

Wash down with a neutraldetergent every 3 to 6months.

Roofs and vertical claddingrequire minimalmaintenance. For otherareas, wash regularlywith a neutral detergent

Common applications On aluminium sheet,extrusions, plate, etc.

On aluminium sheet,extrusions, plate, etc.

Roofing sheet, claddingsheet from coil only.

Corrosion Resistance If correct microns arespecified, excellentresistance against marineand industrial atmosphereattack.

Protects the underlyingsubstrate if correctly treatedprior to coating. Alsoresists UV degradation ifcorrect powder has beenused.

Good corrosion resistance ifcorrect design, fixing,crevice joining, etc.principles are adhered to.

Pre-treatment Finishes Etched, polished,brightened, brushed,sanded, shot blasted, etc.

Matt, satin, gloss speckled,structured, metallic, etc.

Standard gloss level or byspecial arrangements.

Surface Finishes Comparison

9

NOTE: All anodised and powder coated surfaces need regular care depending on the location and installed life. After installation, thesurfaces should only be cleaned with suitably approved cleaning materials. Site repair or changes to colour or finishes requiresexpert opinion.

AlloySeries

Treatment Properties of the anodic layer Typical applications

1000 Surphuric acid anodising,continuous or static

Transparency, reflectivity, brilliance. The lowerthe Fe and Si content, the more transparentthe layer.

Decoration, opticalreflectors.

3000 Degreasing, chemical conversion, food qualitylacquering.Degreasing, chemical conversion, continuouslacquering.Surphuric acid anodising.

Alloys easy to anodise.Protection, decoration, good corrosionresistance, resistance to scoring.

Cans, buildings,domestic utensils.

Hard anodising. The layer has a grayish tint. Engineering

5000 Sulphuric acid anodising, continuous or static.Colourless or electrolytically coloured.

Durable aspect, corrosion protection. Most alloys easy to anodise. The layer is milkyor greyish depending on composition.

Architecture, building.

2000 Chromic acid anodising, sealed withbichromate on 2024 and 2618A.

Surface preparation for adhesive bonding. Aeronautics.

Sulphuric acid anodising, sealed withbichromate on 2017A.

The thickness of the layer is limited and moreor less porous due to dissolved copper.Provides limited corrosion protection.

Mechanical applications.

7000 Chromic acid anodising on 7075.Suphuric acid anodising on 7020.Hard anodising on 7075, 7049A.

Most alloys easy to anodise, those containingcopper, less so.Protection, decoration, harness.

Aeronautics, mechanicalapplications, sportsgoods.

6000 Sulphuric acid anodising, continuous or static;colourless or electrolytically coloured.Electrostatic powder coating.

Most alloys easy to anodise.Working and heat treatment parameters mustbe controlled to achieve consistent appearance mong batches.Decoration, durable aspect, good corrosionprotection.

Metal fittings, buildings,boat masts, transportand many others.

Surface Finishes Comparison

10

What makes a Quality Powder Coating?

The main requirements of a quality coating are:

A uniform and even appearance, properly cured

Excellent adhesion

Excellent weatherability and durability

No fading or chalking when used for exterior orinterior conditions

Minimum 15 year powder manufacturers’ guarantee(exterior applications) and superior quality powderformulations used

Compliance to acceptable industry standards

Colour retention

Following and adhering to these basic guidelines canassure the customer/asset owner of a coating that willdeliver optimum performance while also limiting thechances of coating failure.

TABLE 7: Main Types of Anodising Treatment - for different aluminium alloy series

Overall, anodising is the most common surface finish (havingbeen in use for more than 60 years), but powder coating isincreasing its market share, especially opposite paint coatings.

Anodising and Powder CoatingThe main debate on the merits of different finishes is reallybetween anodising and powder coating as applied toextruded aluminium. Some members of ASFA are bothpowder coaters and anodisers and do not see the twofinishes as competitors. They have different roles to play inenhancing the metal’s decorative visual experience andimproved corrosion resistance.

Wet CoatingAluminium sheeting for roofing and cladding may be anodisedor powder coated in the same way as extrusions but thepreferred method of surface finishing is wet coating of thematerial while in coil form, being more cost effective.

For decorative and corrosion resistant surface finishes anumber of polyester, acrylic and fluorocarbon coatings havebeen developed and used successfully - with service livesexceeding 20 years. These finishes command a price premiumover mill finish price.

What is Anodising?Anodising successfully combines science with nature tocreate one of the world's best metal finishes that is alsoenvironmentally safe.

It is an electrochemical process that thickens and toughens thenaturally occurring protective oxide layer in aluminium. Theresulting finish, depending on the process, is the secondhardest substance known to man, second only to the diamond.The anodic coating is part of the metal, but has a porousstructure that allows secondary infusions (organic andinorganic colouring, etc.)

Anodising is commercially unique to aluminium and its alloys.This surface finish is used for a number of reasons including:

For decoration, through a variety of coloursFor a long-lasting appearanceFor protection against weatheringFor surface hardnessFor abrasion and wear resistanceTo reduce friction and improve repellencyTo improve the adhesion of organic coatings (adhesives,varnish, paint)To modify electrical properties (insulation)To modify visual properties (reflectivity)

Anodising DefinitionsThere are five main types of anodising, each with a range ofpossible processes:

Barrier anodising, used for refined aluminium only, forelectrical applicationsSulphuric acid anodising, used mainly as protection againstweatheringChromic acid anodising for aerospace applicationsHard anodising which increases the surface hardness ofthe metal, mainly for engineering applicationsPhosphoric acid anodising, used to prepare surfaces foradhesive bonding

While the chemical anodising process remains the same for allapplications, the mechanical methods vary according to thephysical types and shapes of metal used.

TABLE 8: Methods of AnodisingProperty Batch or Piece Anodising Sheet Anodising Continuous Coil Anodising

Uses Extrusions, castings, partswith severe forming.

Wide widths, plate, largefabricated products.

High volume, coiled sheet, foil,products with less severe forming.

Advantages Small runs.Thicker films.Anodised edges.

Small runs.Thicker films.Anodised edges.

Wide range of metal and filmthicknesses.Less material handling.Precise colour control anduniformity.Cost effective.

Disadvantages Possible colour variance.Excessive handling.High costs - labour, waterand power.

Colour variance.High costs.Film thickness variance.Crazing when severely formed.

Bare edges on stamped parts.Crazing when severely formed.Limited to sheet and foil.

Typical Anodising Process Flow Chart(performance additives not detailed)

RACKING

COLD WATER RINSE x 2

COLD WATER RINSE

COLD WATER RINSE x 2

ELECTROLYTICCOLOURING (AC)

TIN orCOBALT SOLUTIONS

INORGANIC orORGANIC

DYEING ABSORPTIVE

ANODISE (using DC at18V)10% SULPHURIC ACID

TEMP. 18-22°CCOOLING & AGITATION2 TO 3 min. PER MICRON

DESMUTTING with 20% NITRIC ACID5 - 15 min

CLEANING / DEGREASING (optional)SOAK CLEANER @ ±60°C

ETCHING - CAUSTIC SODA @ ±60°C, 5 - 10 min

Anodising

11

NATURAL

DE-RACKING & PACKING

HOT SEALING in DE-IONISED WATERTemp: 92°C min. / 3min per micron

or COLD SEAL

COLD WATER RINSE COLD WATER RINSE

Suggested SpecificationsFinish: all exposed surfaces should receive an architecturalanodised finish in accordance with SANS 999 (external), SANS1407 (internal) or EN755 as applied to the substrate.

Quality Management systems such as ISO, SANS and Qualanodare applied to assure customers that Finishing companies havethe equipment, the experience and the expertise to produce aresult that will meet the required specification. This applies toall types of coatings.

Finishes must conform to specific requirements in terms of filmuniformity and thickness, seal quality, abrasion resistance, UVlight resistance and accelerated salt spray performance.

The Anodising ProcessAnodising is an electrolytic process that produces a dense,chemically stable protective aluminium oxide film that is anintegral part of the underlying aluminium. This greatly increasescorrosion resistance and its exceptional hardness protects anyunderlying surface finish produced mechanically or chemicallyor by polishing, etching or brightening.

The anodising itself can be achieved through several processes.The sulphuric acid process is most often used for architecturalpurposes because the film produced gives outstandingcorrosion and abrasion resistance, and being transparent, canbe coloured without adversely affecting its excellent properties.

Cross Section of Sealed AnodicOxideThe film thickness before anodising is 1micron. This can beincreased by controlled anodising up to 20 to 25 microns.Recommended thicknesses depend upon the end application.Indoor applications not subjected to heavy wear will accept a5µ thickness. For exterior uses in aggressive environments athickness of 25µ is generally recommended. For very hardcoatings, thicknesses of up to 125µm are produced.

Most films produced by anodising are translucent and so showthe "silvery" look of the aluminium. The coating produced bysulphuric acid anodising can be treated in several ways to give avariety of colours and shades because the anodic film isminutely porous. Anodising companies will provide coloursamples.

Colour matching is dependent on various factors and theseinclude the alloy composition and refraction of light within theanodic film, but colour matching of an acceptable commercialstandard is obtainable by proper attention to specification toensure this is standard practice.

SubstratesThe most suitable alloys for architectural anodised finishes are:Sheet Alloy 1200Extrusions Alloy 6061 and 6063 for etched and mechanical

finishesAlloy 6463 for chemically brightened applications

Castings Al 99,5 / LM0 and CEN 51000 / LM5Not all welding is suitable for anodising ( 5 series rods preferred).Seek advice. Contact your anodiser for further information.

Important informationBefore agreeing to have material anodised, it is important forthe purchaser to discuss process parameters with the Anodiser.Such parameters include:

Minimum and maximum rack lengths.Jigging effects, especially on precut and long items.Possible colour variations.Any critical surfaces.Effect of moisture and packaging (especially adhesives) onthe uncoated surface.Minimum order size / value.

Anodising

SPECIFY...Finish appearance (bright, matt. coloured, etc) alloy andend use of product and any special packaging required.

Anodic Film Inland 15µThickness Coastal 25µ

InorganicColour Natural

or Light Bronze 541Bronze 543Dark Bronze 545Very Dark Bronze 547Black 549

or Organic

SANS Standards

External FinishesAnodised finishes to be in accordance with SANS 999,current date - Anodised coatings on aluminium (forarchitectural applications)orInternal FinishesSANS 1407, current date - Anodised coatings onaluminium (for general applications)

Protective Low tack adhesive tape,Coating for but remove promptly orInstallation oil surfaces

AnodiserTo be a certified markholder of SANS 999 and/or SANS 1407 and/or ISO 9000/14000 or at least conformingto SANS 999/1407 standards in terms of reference,Qualanod certification may also be relevant.

12

Aluminium Hydroxide Seal

Colouring Matter (in oxide pores) -depth varies with colouring process.

Aluminium Oxide Coating (5 - 25µm)Aluminium Metal

The Anodised Surface

Anodising

13

Anodising Characteristics of Cast Aluminium

Alloy Designation Suitability for AnodisingProtective Colour Bright

Alloy Type

LM5 - CEN 51300LM6 - CEN 44100LM10 - CEN 51200LM16 - CEN 45300LM20 - CEN 47100LM24 - CEN 46500LM28

E E GF U UE F UG F(D) UG F(D) UF F(D) UU U U

Al Mg5Al Si12Al Mg10Al Si5 Cu 1 MgAl Si12 Cu FeAl Si9 Cu3 FeAl Si18 Cu Mg Ni

E = Excellent, V = Very Good, G = Good,F = Fair, U = Unsuitable, D = Dark Colours Only

Source of Defects in AnodisedSurfaces

Defects originating during work piece preparation -yielding stains, striping and cloudiness and also spottydiscolouration.Defects originating from anodising itself - yieldingrainbow colouration, corroded appearance, spotty film,uneven film, discolouration and hairline cracks. Also burntspots.Defects originating during colouration - colour variation,mottled colours (light and dark), not abrasion resistant,colour not lightfast and colour cloudy.

Bright AnodisingOffers architects and designers more than standardarchitectural colours.Popular choices include bright silver, gold and brass butother colours such as bronze, black, blue and red areavailable. Not all colours are light and weather fast.Used extensively in the lighting industry and also for shopfront and partitioning extrusions.Most common process is chemical brightening, whichrequires great care not to damage the material to bebrightened. Extrusions are often polished to removescratches before brightening.

Summary of Anodic FilmProperties

Resistance to corrosion against a variety of atmospheresand environments.

Suitability for manufacture and packaging of foodstuffs.

Suitability for consumer durables and cooking utensils.

Offer of a variety of colours for external and internalapplication.

Enhancement of optical properties such as reflectivity /brightness.

Specular reflectivity of +85% can be achieved.

Heat reflectivity and emisivity are transformed toextend aluminium’s usefulness in many industries involvingheat radiation and heat transfer.

Bright aluminium reflects over 80% of light and about90% of heat radiation that falls on it.

Good electrical insulating properties (in contrast toaluminium itself) - providing insulation with no bulk andcapable of withstanding heat - useful in condensers andtransformers.

Forming operations should be carried out beforeanodising to prevent cracking.

Anodising Characteristics of Wrought Alumnium

Alloy Designation Suitability for AnodisingProtective Colour Bright

AlloyType

1080A1050A12002xxx310331055251500550835454606364637020

E E V - EE E VV V GF F(D) UG G FG G FV V G - VE E EV V GV V GG G FE E VF F U

Al 99,8Al 99,5Al 99,0Al Cu Si MgAl MnAl Mn MgAl Mg2Al Mg1Al Mg MnAl Mg3 MnAl Si Mg MnAl Mg SiAl Zn Mg

Note: The various forms of semi-fabricated aluminium have their own characteristics affecting the anodising finish. Different alloysanodise to slightly different shades.

Anodising

14

The thickness of the aluminium oxide coating can be varied by the anodising process time. The following figuresare usual:

5 Micron Suitable for decorative applications, jewellery, arts and crafts.

10 Micron Suitable for internal applications, and outdoor applications where cleaning is veryfrequent, for example, caravan trim. Also for reflectors.

15 Micron Recommended for the majority of ordinary internal architectural requirementsand metal fittings of every sort.

25 Micron Recommended for heavy duty external permanent architectural applicationswhere little deterioration can be tolerated. Also for kitchen utensils and marineenvironments.

25 Micron plus to 250 Micron(125 Microns max. is more usual)

25 Micron to 250 Micron is achieved by Hard Anodising of wrought alloys done byvarying the electrolyte composition and modulating the process parameters. Hard anodic films are used to provide abrasion resistant surfaces on bearings, pistons,gears and other components.

Anodising and ColourWet Surface Coating - on pretreated, grounded substrate:colour shades unlimited, various degrees of gloss. Lessresistant than anodised surfaces. Flaking possible. On siterepairs possible. Overall chemical resistance dependant onbinder type and pigment quality. Chalking observable.Inorganic dying - with colour matter (heavy metalhydrates) incorporated in coating outer region. Colourspale to dark bronze and gold tones, muted. No flaking.Onsite repairs impossible unless using a surface coating.Organic dying - with coating inseparably bound to thealuminium. Spectral colours - deep yellow, red, blue, black -but no brown, bronze or grey. High brilliance. No flaking.Colours distinct.Electrolytic coating - dying with metal salts, colourinseparably bound to the aluminium at the base of thepores. Colours brown, bronze, grey, slate, pink, burgundy.No spectral colours, no white. No chalking or flaking.Electrolytic colouring, combined with organic dying - onecolour at base of pores, the other incorporated in thecoating. Virtually unlimited colour, muted shades,no white.Hard anodising colours are limited to grey and brown.Alloy elements and impurities influence colour in theanodic oxide film.

Anodised Aluminium ApplicationsStructural and architectural categories of all types - interiorand exterior.Commercial and residential building products.Applicances and furniture, computer hardware andexhibition displays.Food preparation equipment.Sporting goods and boats.Motor vehicle componentsAn almost endless array of products for everyday life!

IntroductionPowder coating is an advanced method of applying a decorativeand protective finish to aluminium - creating a wide range ofproducts that are used by both industries and consumers. Theprocess result is a uniform, high quality and attractive finish.The powder coating industry continues as the fastest growingfinishing technology in North America. Powder costs less toapply than equivalent performance liquid paint.

Attributes of Powder CoatingTough and durableExcellent corrosion resistanceImpact resistantAttractive and colourfulExcellence of finishHigh quality and versatileSolvent free and environmentally friendly

The list of products powder coated is extensive and includesautomotive parts, industrial piping, appliances, sports goods,outdoor furniture, power tools, aircraft parts, office equipmentand architectural fittings such as windows, doors, showers, etc.

Powder Coating ProcessThe pre-treated aluminium components are racked to aconveyor, which is earthed. A powder spray gun is set toproduce a cloud of powder particles with a strong electrostaticcharge. The charged particles are attracted through theelectrostatic field to the face of the product and to the sides andback along the lines of force in the electrostatic field. After thepowder has been applied, the coating is stoved attemperatures specified by the powder manufacturer.

Range of ColoursPolyester powder coatings are available in a vast range ofcolours. These may be specified from the international RALcolour chart, SANS 1091 or the individual colour ranges ofpowder manufacturers and coaters. Specifiers should alsospecify the gloss level required, with a matt surface beingpreferable for most architectural finishes.

For exterior use, specifiers should at least opt for finishes inaccordance with SANS 1578 and 1796, as these not onlyprotect the substrate metal against corrosion, but also resistUV degradation as well.

Versatile FinishesPowder coated surfaces are more resistant to chipping,scratching, fading and wearing than other finishes. Colourselection is virtually unlimited with high and low gloss, metallicand clear finishes available. And colours stay bright and vibrant.Texture selections range from smooth surfaces to a wrinkled ormatt finish and rough textures designed for hiding surfaceimperfections. Powder coating is a technology of the future!

Powder Coating

15

Quality Standards

What factors should be addressed and clearly defined whenspecifying architectural aluminium finishes? The importanceof clear technical specifications cannot be emphasizedenough because, at the end of the day, a professionalreputation may be at stake and costly disputes could arise.

Here is a handy check list of key elements that should beaddressed:Material type:Aluminium alloys produced to BS1470, 1471 or 1474.Significant Surfaces:Details which surfaces will have nominal 50-80 microns.Colour:

As agreed upon from RAL or NCS standard colour chart.Fabrication:

Detail any peculiar or difficult factors relating to thefabrication requirements.

Type of Powder: Polyester, equivalent or better.Gloss level: Gloss, matt or satin.Applicator:A certified SANS 1796 approved applicator.Process Control:

Strictly in accordance with SANS 1796 or Qualicoat.Certification:

Certificate of Conformance will be provided by anapproved applicator on completion of the coating.

Pre-treatment

Degreasing, rinsing,caustic etch, rinse,

nitric acid desmutting,rinse, chromate

conversion, rinse,sealing rinse with

demin water.

Dry off / Cooling

Powder coating

Heat Curing160° C to 210°C

Cooling

Parts unloading

Process Flow Diagram (for aluminium)A typical process flow block diagram for a powder coating line.

The objectives of pre-treatment of metal surfaces are:Removal of impurities including soil, welding splatter,scale, grease and oil.Conditioning of the surface for optimum adhesion ofthe coating film.Obtaining uniformity throughout the entire treatedsurface of the substrate.

Environmentally AdvancedThe powder coating process is also environmentally friendly asit is virtually pollution free. Unlike liquid paint, no solvents areused so only negligible amounts of volatile organic compounds(VOC's) are released into the air. In addition, unused or over-sprayed powder can be recovered so any waste isminimal and can be disposed of easily and safely.

AdvantagesThere are many advantages that make the choice of applyingthermosetting powder coatings attractive to the coatingcompany. These include:

Powder is immediately ready for useLess powder wastage during the application processReduced health hazard in case of exposure of operatorsSuperior cured-film propertiesLower capital investment costs

Powder Coating of AluminiumImportant Information1. Surface Finish of Raw MaterialWhile they have excellent flow properties, polyester powderswill only partially smooth out imperfections in a metalsubstrate. It is essential that any component must be supplied inthe raw state, with a surface condition that reflects the ultimatesurface required. (Aluminium must be packed with care duringtransport to avoid scratching and marking).

2. Jigging PointsTo apply polyester powder it is necessary to hang each item onto a conveyor and so one or more jigging points are required.These are best in the form of drilled holes or suitable jiggingedges, where the contact point does not affect the appearanceof the finished product.

3. Pretreatment DrainageAll of the approved pre treatments require immersion in

Powder Coating

SPECIFY...Colour RAL / NCS SANS Standards

or SANSor Mfr’s Powder coated finishes to be in accordance with SANS 1578.

range Organic powder coatings for external architectural aluminium

Finish Glossor Satin Powder Coateror Matt

To be a certified markholder of SANS 1796 and / or an applicatior approved by thePowder Coating powder manufacturer who must be a certified markholder of SANS 1578: Organic Film Thickness 60 - 80µ powder coatings for external architectural aluminium.

Protective Coating Low tack Guarantee of coating given by the Powder Coating manufacturer is only validduring adhesive provided the applicator is approved by the coating manufacturer.installation tape

16

Powder Coating

17

aqueous solutions. It is therefore necessary that componentsdo not float or retain trapped solutions after treatment. Hollowcomponents may cause ingress of solutions that can boil outduring the powder curing cycle, spoiling the coating.

Most components can be suitably ventilated by a 6mmdiameter hole at a point permitting total drainage of thecomponents.

Large flat butting surfaces can also trap solutions by capillaryaction and these should be avoided.

Sound deadening or porous filling materials that can absorbpretreatment chemicals or materials likely to melt below250ºC should not be built into an assembly before coating.

4. Powder (uneven surface) PenetrationPowder initially adheres during coating by electrostatic forces,but a phenomenon known as "Faraday Cage" can counter theaction on components with narrow recesses, slots or sharp,enclosed corners. Advice should be sought where these can beavoided, but generally with slots, the width between the twoedges should be greater than the depth.

5. Dissimilar MetalsAssembles consisting of different metals or painted surfacesshould be avoided. The different materials may require non-compatible pre treatments and electrolytic corrosion may alsobe encouraged.

6. Heavy MassesHeavy components require a longer heating cycle due to themetal temperature being the important criterion.Consequently, these are more expensive to coat. The surfaceappearance (but not colour) of the finished item may beslightly different between substrates of differing mass due tovariations in "heat-up" and cool down times.

7. Exposed SurfacesAll drawings should indicate the area where the coating isrequired.

8. Protective TapeThough polyester powder is an extremely tough and resilientcoating, mechanical abuse can cause unsightly scratches andblemishes. Obviously the best way to eliminate this is byadopting good working practices both during fabrication andinstallation. Not withstanding this, protective tape is usedextensively for the protection of architectural products.

9. ApplicationProtective tape is normally applied by the fabricator or windowmanufacturer. The powder surface to which it is applied mustbe free from dirt, oil, cement or other surface contaminates. Ifnecessary, the surfaces can be cleaned using a soft clothdampened in white spirit. The surface must be dry before tapeapplication.

10. Cleaning of residual adhesiveWhere necessary, any residual adhesive left on the powdercoated surface following the removal of protection tapes shouldbe removed by wiping with a white spirit dampened cloth.Solvents or cleaning solutions containing esters, keton,chlorinated hydrocarbons or alcohols must not be used. It isalways recommended to try these procedures on a small areafirst.

Critical tests any powder coater ofrepute must be able to conduct on theirpremises:

Adhesion test (Impact, cross hatch, bend and pressurecooker)Reverse impact (cure result)Permeability (correct pretreatment)Permascope (correct film thickness)Gloss meter reading

Wet Coating

SPECIFY...AlloyTemperNominal Coil ThicknessProfileSurface Finish mill

stucco embossed

Colourfrom coil coater’s range

Gloss

Top side coating PVDFPolyesterAcrylic

Bottom side coating As top sideor light greyprotective lacquer

18

IntroductionWhile anodising and powder coatings are thefavoured surface finishes for extrusions,aluminium is also available in flat sheets in a wideassortment of colours. Aluminium sheet is coatedwhile in coil form. The process is very economical.

Wet coated or painted aluminium provides aflexible finish that is tough and durable. Througha sophisticated production process, the colour isbonded onto the aluminium. This means that thesurface finish can stand up to even severeforming techniques (beading, stamping, embossing,deep drawing) without cracking or flaking. Thisis the most important advantage of coil coatedaluminium - with coating thicknesses of25 - 28µm - thanks to a careful match betweenthe alloy and the coating strip.

ApplicationsFor decorative and corrosion resistant surface finishes a largevariety of paint systems and colours are available includingalkyd, acrylic, vinyl and epoxy coatings as well as fluorocarbons- with service lives exceeding 20 years.

Painted aluminium coil is a natural choice for the buildingmarket with coating types designed to meet the variedrequirements and applications of the market. A wide range ofalloys, tempers, coating types and colours are available for allthe different cladding and roofing systems in use today and themany different fabrication techniques employed. Painted coil isalso used in vehicles.

The coil is usually coated on one side with a decorative coatingand on the reverse with a suitable wash coat - though bothsides can be coated if required. Cleaning, pre-treatment andcoating are done in a continuous operation at speeds of over150m per minute. The coating can be electrostaticallydeposited and normally, it is oven dried.

As the aluminium is cleaned, treated and painted while flat, theresult is a uniform finish and coating thickness.

Coils are produced in various widths and thicknesses to suitdifferent applications. All are suitable for roll-forming intovarious profiles for roofing, cladding and awnings, as well asrainwater goods such as guttering. Flat material is used forsignage or converted into cladding panels.

Process Flow Diagram

IntroductionAs with all materials exposed to the elements, regularmaintenance is required to ensure maximum life andperformance from the product.

A key to successful cleaning depends on the knowledge of whattype of surface finish you are dealing with. The life of ananodised, powder coated or painted surfaces can be greatlyenhanced by applying a regular maintenance programme. Thiswill ensure the removal of any dirt, grime, grit, atmosphericpollutants and iridescence.

Any chemical attack on a decorative surface that is notregularly cleaned becomes increasingly severe and afterseveral years, the finish may prove impossible to restore.

Cleaning ProcedureA regular cleaning and maintenance system is essential for tworeasons:

To maintain decorative appearance; andTo reduce any chemical attack, if applicable.

The cleaning procedure may be broken down into threedistinct categories, namely:

1. Primary Cleaning:Primary cleaning is the initial cleaning that should occur afterinstallation / completion to remove atmospheric dust, depositsof dirt, possible cement deposits, glues, etc.

2. Secondary Cleaning:This is normally a heavy duty clean that is carried out on asurface that has not been cleaned for some time.

This is carried out by companies that specialise in the cleaningof facades, windows, doors, curtain walling, etc.

The most important criteria of an aluminium cleaning agent isthat it should not be toxic, have a pH within 4,5 and 9 and itmust be free of fluorides, chlorides or sulphates.

3. Periodic Cleaning:This is the cleaning cycle that should be done on a regular basisAFTER the primary and secondary phase (in the case of a newinstallation, it follows after the primary). The intervals of eachcleaning cycle are dependent on the atmospheric pollutants,area, region, corrosion levels, etc. for a particular region -approximately three months at the coast and six months inland.

Care and Maintenance

Guidelines for the Protection of Aluminium

DO'S:Protect exposed aluminium surfaces until all the tradesetc. have been completed.Any cement or acid should be removed as soon aspractical. This will prevent any chemical attack.When cleaning, wash down all surfaces with a neutraldetergent and rinse thoroughly.Remove stubborn deposits on ANODISED aluminiumwith a suitable nylon abrasive cleaning pad or brush, plusneutral detergent and then rinse.Remove stubborn deposits on POWDER COATEDaluminium with a suitable soft cloth or nylon brush, plusa neutral detergent and then rinse.To clean long neglected areas, it is advisable to useproprietary cleaners specifically formulated foraluminium surfaces. These products contain residualwaxes etc. and can substantially improve the appearanceof worn or weathered surfaces.

DONT'SUse wire brushes, steel wool, blades or emery paper.These are NOT recommended under any circumstances.Avoid mechanical damage from scaffolding and badhandling.Allow cleaning with pool acid on anodised finishes (as itcontains chlorides).Allow cleaning with abrasive pads on powder coatedsurfaces.Allow mortar cleaning chemicals to come into contactwith powder coated and/or anodised surfaces, unlessthe cleaning company gives a warranty for its product.Aluminium should not be in direct contact with brass orcopper, which may be wetted.Allow strong alkalis such as caustic soda, lime etc. tocome into contact with aluminium or finished aluminium.

19

For more information on protection of aluminiumsurface finishes during manufacture, transport, coatingand installation, contact AFSA or any accredited surfacecoating company.

Tel: (011) 453 3339Fax: (011) 453 3403

E-mail: afsa@afsa.org.zaWebsite: www.afsa.org.za

Acknowledgements for the contribution of ideas, material and/or pictures to:AFSA Library E.S. Mowat and SonsAkzo Nobel / Interpon Powder Coatings Hulett AluminiumAstro Anodizing cc Hulett-Hydro ExtrusionsCascolor Aluminium Finishing Lite-Epoxy Coating ccContinental Anodisers Polynam (Pty) LtdC.S.I.R Standards SA (SABS)Design Anodising Wispeco (Pty) Ltd

1. “Aluminium Handbook 2”, Section 3 byAluminium Verlag

2. AFSA Aluminium Surface Finishing Manual,previous edition; and the Anode anodisingbrochure

3. Pechiney website4. American Anodizers Council (AAC) website5. Aluminium News (AFSA publication),

various volumes6. Aluminium Coil Anodizing (ACA) website7. “Complete Guide to Powder Coatings”,

Akzo Nobel / Interpon Powder Coatings8. Cascolor / Alufinish website

9. British Anodising Association (BAA) Guideto architectural and industrial anodising

10. Wispeco Aluminium Extrusions manual(pages 13 to 17)

11. “Care of Aluminium” by the AluminiumAssociation Inc.

12. “Surface Finishing of Aluminium Alloys”,Alcan Australia

13. Aluminium Extrusion Council (AEC) website14. North American Powder Coating Institute

(PCI) website15. Diverse array of articles on surface finishing.

REFERENCE SOURCES USED IN THE COMPILATION OF THIS GUIDE:

AFSA has a number of reference sources on surface finishing of aluminium and its alloys. Members and non-membersare welcome to contact AFSA for more information (which is free to members).

AFSA / ASFA Membership:For a current list of AFSA or ASFA members, please contact AFSA as shown below:

This revised edition was compiled by AFSA (in conjunction with There Be Dragons)and published by the Aluminium Federation of Southern Africa. © 2004

Aluminium Federation ofSouthern Africa