The Basic of Airless Spraying

Coating Material4 Basic Components

Binder, Resin, or Polymer Pigment Solvent Additives

Viscosity

Solid by Volume/Solid Content Low Solids = 20-30% solids Medium Solids = 30-50% solids High Solids = Up to 100% solids

Methods of Coating Application

Brushes Rollers Sprayers

The choice of an application method depends on the type of coating to be applied, the type and size of surface to be coated, and governing environmental regulations. However, the consistency of some coatings may dictate a particular method. For example, coatings that are excessively viscous may not permit effective application by spray; or a low viscous coating may only be effectively applied by spray. Either the specifications or the manufacturer's instructions usually will indicate the preferred application method. All application methods have inherent advantages and limitations.

*) other methods: electrodeposition/electrocoating (E-coat), autodeposition, dip/flow/curtain coating,

BrushMethods Advantages Limitation

Brush • the ability to stripe coat• best for oil-based and waterborne

coatings, or slow-drying coating• most common, particularly around

irregular surfaces such as rivets, bolt heads, piping, railing, and similar areas• low investment, low technology• independent of power• it aids in thorough wetting of the

substrate, particularly on surfaces that are porous• can be used in restricted spaces, be

useful for small areas, with less wastage and contamination of surroundings. • no loss through overspray • short set-up time

• slow, low productivity, • labor intensive• may not produce a uniform coating

thickness• not practical for large surfaces• may leave unsightly brush marks• not recommended for fast-drying &

high solid coating (i.e. vinyl zinc-rich and epoxy zinc-rich coatings that need agitator to be kept in suspension during application)

Roller Methods Advantages Limitation

Roller • excellent for large, flat areas (e.g., tank sidewalls and tops, decks, ship hulls, walls, and ceilings) or whenever application does not require the skill needed for brush or spray application• recommended for use in windy

conditions to eliminate excessive material loss and overspray• may be used for indoor application

when overspray cannot be tolerated.• Twice faster than brush application

• Roller application characteristics for high solids coatings and inorganic zinc rich coatings are considered poor. High performance coatings/linings for immersion are seldom applied by roller because of non-uniform thickness and wicking caused by roller nap residue.

• demands suitable rheological properties of the paint.

SprayerMethods Advantages Limitation

Spray • speed of application • control of film thickness • allows the use of fast drying coatings • uniform finish • can be installed as an automatic process• more cost effective in the long run

• overspray & solvent emission = health hazard• does not properly fill cracks or seal

most rough surfaces• requires more skilled operator• requires more maintenance•medium/high investment cost• considerably more waste, need serious

handling

Types of Spray Painting

Type Pressure Advantages DisadvantagesAir spray /Conventional

Max 7 bar • Very good finish achieved• Good control ability• You can use small amounts of material

• Poor transfer efficiency: 60% waste (overspray)• Slow application rate• Can only spray low viscosity paints

HVLP(High Volume Low Pressure)

Max 0.7 bar • Approximately 80% efficient vs. air spray• Good paint saving• Environmentally friendly• Far cleaner application, & less

maintenance

• Slow application rate• Low viscosity materials only can be

sprayed

Airless Max 500 bar • Fast application - 200 to 250 M²/hour• Good transfer efficiency• Application of high build coatings• High film build

• Poor control• Reduced quality of finish Incapable of partial triggering Susceptible to “tails” Fluid injection hazard Spray gun tip wear

Air Assisted Airless /Airmix / Aircoat

Max 400 bar •More control, high production rates•Better transfer efficiency•Better quality finish• reduced wear on fluid nozzle and pumps

No partial triggering Requires extra air hose Fluid injection hazard Susceptible to lower transfer efficiency

than airless due to improper setup of air and fluid pressure

Electrostatic • Greatly reduced overspray• Paint saving• Low booth maintenance• Labor saving• Less spraying ability required

Spray equipment more expensive Can produce minor shocks Electrostatics can be easily deactivated

and thereby become more inefficient Ungrounded areas will repel coatings Requires good ground, <1 meg ohm

X70 Light CartX50 X40

X70 Heavy-duty Chart

Why Plural Component Airless Sprayer?

• Almost 90% of today’s coating materials are plural components, but applied with single component sprayer.• Today’s “solventless” coatings are high in viscosity. When 100% solids

components are mixed, then cross-link to form a solid. There is no solvent to act as a “heat sink” and slow down the reaction. Reaction is subject to heat generation (exothermic reaction) that shortens an already short pot life. Larger quantities generate greater heat, leading to shorter pot life. Plural Component system are usually equipped with heaters to reduce viscosity.• 100% SBV or solvent-free coating material:

– Epoxy: A two-component material that mixes a base (resin or epoxy) with an activator (catalyst, hardener, or converter).

– Polyurethane: A two-component, fastset coating formed by reacting (or mixing) an isocyanate with a polyol resin.

– Polyurea: A two-component fast-set coating that is formed by reacting an isocyanate with an amine resin.

Plural Component Airless Sprayer

The base and activator are pumped to a mixer manifold or plural component spray gun separately. They are then mixed and applied immediately to the work piece via the spray nozzle.Advantages– Labour saving– Material saving– Guarantee of correct mixing– Allows short pot life materials to be applied

Disadvantages– Can be difficult to use

XP35 XP50XP70

XM70

XMPFPXM50

Plural Component Airless Sprayer

Reactor E-30i

Reactor H-XP2

Reactor E-XP1

Fast Set Curing Plural Components Sprayers

Plural Components Sprayers Accessories

Standard heater(Viscosity Control)

Externally controlled Viscon

Complete Viscon HF Heater with Manual Thermostat Control

Gun Splitter

Electric heated hose

Water-jacketed Heat Hose

Remote manifold

Mix manifold

Heated Hose Controller

Hopper

XTR 5

XTR 7

Fusion gun

Probler gun

Spraying is simple but you must have the right equipment

What types of materials will you spray? Now and in the future?The types of materials you spray will determine the size of the tips you use. If you plan to spray a variety of materials you have to consider buying a sprayer with more versatility.

How many gallons per week will you spray?Purchasing a part-time sprayer to do a full-time job has disappointed many contractors. In the long run, saving money on a sprayer that is inadequate for the job, or not durable enough, will cost a lot in lost labor.

What power sources are available? Will most jobs be indoors or outdoors?Your answers will help choose a unit family (gas, electric, or compressed air)based on power sources alone.

What types of surfaces will you be spraying?Will you be spraying on drywall, exterior siding, or concrete? You have toconsider the tip sizes needed as well as the quality of finish required in order tochoose the best sprayer for the job..

Spraying is simple but you must have the right equipmentHow many spray guns will you use at one time, now and in the future?If you plan to use more than one gun at a time, then you have to purchase a unit that has the ability to handle multiple guns.

What types of jobs will you bid?Each job has its own requirements. New construction, maintenance work, and commercial jobs all vary in terms of: coatings used, crew size needed, and power sources available.

What hose lengths will you use?Hose length depends on the job site, material being sprayed, tip size, and hose diameter. Your sprayer must be able to support the length of hose.

How much do you want to spend on a sprayer?Buying a sprayer is an investment. You do not want to over-buy or under-buy. Keep in mind the cliché, “You can pay now or pay later”. Downtime resulting from an undersized, overworked sprayer or poor quality equipment can quickly wipe out any savings from the initial low purchase cost of the sprayer.

Airless Spraying TechniquesAdjusting the Pressure

It is best to spray at the lowest pressure that completely atomizes the coating. The pressure control should be set at a low-pressure setting and slowly increased until the paint is completely atomized. If the spray pattern has fingers or tails, then the pressure should be increased.If the maximum pressure of the sprayer is not enough to achieve a good spray pattern, a spray tip with a smaller orifice should be used.

Airless Spraying TechniquesAiming of the spray pattern

The spray gun should be held approximately 12 inches (30.5 cm) from the surface, and aimed straight (both horizontally and vertically) at the surface. Extremely large tips will require you to move further away to achieve a goodspray pattern.

The spray gun should move across the surface with the wrist flexed to keep the gun pointed straight at the surface. “Fanning” the gun to direct the spray at an angle will cause an uneven finish.

Airless Spraying Techniques

Triggering TechniqueThe spray gun should be triggered after beginning the stroke (lead stroke) and released before ending the stroke (lag stroke). The gun should move during both the trigger squeeze and trigger release. This technique prevents blotches of thick coating at the beginning and end of each stroke.

Overlapping TechniqueThis technique ensures that an even amount of coating has been sprayed onto the surface. The spray gun should be aimed so that the tip points at the edge of the previous stroke, overlapping each stroke by 50%.

Common Spray Technique Errors

Pressure Set to HighIt is easy to just crank up the pressure control to the maximum and slap on thematerial. For professional results, turn down the pressure as low as you canwithout getting tails. You will:

– Reduce wear on your pump– Reduce wear on your spray tip– Spray a more consistent even finish– Reduce the amount of overspray (wasted paint)

Holding Down the Trigger too LongIt is easy to just pull the trigger and keep moving up and down or side to side, overlapping and moving down the wall spraying constantly. If you are not triggering the gun every time you change directions you will have at least double the mil thickness in every spot you change directions. In the right light or over time, your customer may be able to see these heavy areas. As explained earlier, you should trigger the gun on each stroke and be moving into and out of each trigger pull.