7/22/2019 Anodising Information

1/2

INFORMATION SHEET

Mp (Eastern) Limited

Trinity RoadSuffolk

UK

This document is provided for information purposes only. Page 1 of 2

Anodising

The electrolytic oxidation of aluminium is known as anodising, by electrolysing

suitably prepared aluminium in an acid solution (typically sulphuric or chromic acid),

the surface layer of the aluminium can be converted to a coating with protective,decorative or functional properties.

The coating formed is analogous to a honeycomb and will accept dyes of different

colours, anodised aluminium is generally sealed after processing, this sealing seals the

porous structure of the aluminium oxide and improves corrosion resistance, sealing

can be carried out in a variety of different solutions, including hot water, low

temperature nickel sealing and sealing with dichromate solution.

The substrate composition and condition (alloy type, grade temper etc), have a

significant effect on the anodising characteristics of the components and the

subsequent finish obtained, with different materials requiring different processconditions, consequently it not recommended to mix alloy types during the same

process run, alloys must be strictly segregated and identified before processing.

The alloy type also has a bearing on the post anodising appearance, with the final film

colour dependent upon a number of interacting factors, including, alloy composition

and form of supply i.e. cast or wrought , surface finish, pre treatment prior to

anodising type of anodic film (sulphuric, hard or chromic) and anodic film thickness.

When specifying anodising on drawings or orders it is recommended that wherever

possible national, international or defence standards are used to provide the

processing instructions to your supplier, typically the following information shouldalso be provided;

Specification reference Base material composition and condition Significant surfaces and areas where measurements of coating thickness are to

be made.

Any areas that must not be used as contact points for jigging/wiring Any special inspection requirements Any special packing requirements

You can find more details with explanations why this information is important in the

Information sheet: Order information.

7/22/2019 Anodising Information

2/2

INFORMATION SHEET

Mp (Eastern) Limited

Trinity RoadSuffolk

UK

This document is provided for information purposes only. Page 2 of 2

Specifications

The common UK standards used for specifying anodising are summarised in table

form below for information purposes only.

MP Eastern have a large library of obsolete/superseded, international and customerspecifications, call us if you are having difficulty obtaining relevant information, we

may be able to help. Call us on 01502 573047 or e mail sales@mpeastern.co.uk

British standards for specifying anodising

Standard Notes Comments

BS EN 12373-1:2001 Sulphuric anodising;

Film thickness is specified by referring to a specific class;Class 5 Min av thk 5 m

Class 10 Min av thk 10 m

Class 15 Min av thk 15 mClass 20 Min av thk 20 m

Class 25 Min av thk 25 mSurface preparation before anodising is designated by the

symbols E0 to E8

Sealing either Hot water or nickel sealing as specified.

Supersedes BS 1615

BS EN 2101:1991 Chromic acid anodising;Alloy category 1 Min film thickness 2.5 m

Alloy category 2A Min film thickness 1.5 m

Alloy category 2B Min film thickness 1.0 mSealing; Type A = Unsealed, Type B = Hot water sealed,

Category 2 alloys shall preferable be dichromate sealed

Aerospace series

BS EN 2284:1991 Sulphuric acid anodising;Class A Unsealed anodising

Class B Sealed anodising

Thickness class 1 12 to 25 mThickness class 2 6 to 12 m

Sealing as specified; Dyed aluminium hot water seal,

Undyed aluminium hot water seal or dichromate seal.

Aerospace series

BS EN 2536:1995 Hard anodising;Category 1 alloys < 1 % Cu : 30 m to 120 m film thickness

Category 2 alloys 1% to 5% Cu : 30 m to 60 m film

thickness.Note: Restrict thickness on splines & threads to 25 m

Sealing is specified either hot water or dichromate seal

Aerospace series

BS 5599:1993(2002) Hard anodising;Unless otherwise specified on the drawing or order thickness

shall be 40 to 60 m, sealing shall be as specified.

Supersedes Def Stan 03-26

Defence standards for specifying anodising

Standard Notes Comments

Def Stan 03-24/5 Chromic acid anodising; Superseded Def 151 Type 2

Def Stan 03-25/5 Sulphuric acid anodising;Unless otherwise stated on drawing or order film thickness 8

to 13 m, i tems that are to be dyed black may have a coating

thickness