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Fundamentals of Corrosion
Other pretreatments use aqueous chemical solutions that are applied by
immersion or spray techniques. These chemicals prepare the substrate surface to accept the coating and to improve adhesion. Different metals are
treated in different ways.
7.6.2.1 Aluminum
After the aluminum substrate has been treated to remove oily soils and
corrosion products, it is pretreated using chromate conversion coating and
anodizing. A phosphoric-acid-activated vinyl wash primer, which is also
a pretreatment, must be applied directly to the metal and not over other
pretreatments.
7.6.2.2 Copper
After cleaning by solvents and chemicals, the surface is abraded to remove
corrosion; bright dipping in acids will also remove corrosion. Chromates and
vinyl wash primers are used to pretreat the cleaned surfaces.
7.6.2.3 Galvanized Steel
To prevent white corrosion, the mill applies oil and wax to the galvanized
steel surface, which must be removed. After cleaning, chromates and phosphates are used to pretreat the surface. If no other pretreatment has been
utilized, a vinyl wash primer can be used.
7.6.2.4 Steel
Phosphate pretreatment is usually applied to steel to provide corrosion resistance after cleaning to remove rust and oily soils. Chromates and wash primers are possible alternative pretreatments.
7.6.2.5 Stainless Steel
Under normal circumstances, stainless steel is not usually coated because
of its corrosion resistance. If it is to be coated, oily soils must be removed
and the surface abraded to produce roughness. Wash primers will improve
adhesion.
7.6.2.6 Titanium
Cleaned titanium is pretreated the same as stainless steel (see above).
Fundamentals of Corrosion
Other pretreatments use aqueous chemical solutions that are applied by
immersion or spray techniques. These chemicals prepare the substrate surface to accept the coating and to improve adhesion. Different metals are
treated in different ways.
7.6.2.1 Aluminum
After the aluminum substrate has been treated to remove oily soils and
corrosion products, it is pretreated using chromate conversion coating and
anodizing. A phosphoric-acid-activated vinyl wash primer, which is also
a pretreatment, must be applied directly to the metal and not over other
pretreatments.
7.6.2.2 Copper
After cleaning by solvents and chemicals, the surface is abraded to remove
corrosion; bright dipping in acids will also remove corrosion. Chromates and
vinyl wash primers are used to pretreat the cleaned surfaces.
7.6.2.3 Galvanized Steel
To prevent white corrosion, the mill applies oil and wax to the galvanized
steel surface, which must be removed. After cleaning, chromates and phosphates are used to pretreat the surface. If no other pretreatment has been
utilized, a vinyl wash primer can be used.
7.6.2.4 Steel
Phosphate pretreatment is usually applied to steel to provide corrosion resistance after cleaning to remove rust and oily soils. Chromates and wash primers are possible alternative pretreatments.
7.6.2.5 Stainless Steel
Under normal circumstances, stainless steel is not usually coated because
of its corrosion resistance. If it is to be coated, oily soils must be removed
and the surface abraded to produce roughness. Wash primers will improve
adhesion.
7.6.2.6 Titanium
Cleaned titanium is pretreated the same as stainless steel (see above).