Painting Brass
Q. I have a design that requires the use of brass (No. 360 copper alloy). This
design requires that some portions be painted (epoxy primed and polyurethane
topcoated). I have no experience painting brass and/or know if this alloy is
even “paintable.” Could you provide some insight into this matter
and recommend how to best prepare the surface for painting? P.S.
A. Painting brass is a piece of cake if the surface is properly prepared. As
with cake, brass pretreatments come in different flavors. However, all cakes
start with batter, and all brass pretreatments start with cleaning.
Brass can be cleaned using solvents, aqueous chemicals or emulsions. The metal
must be cleaned to remove oily soils that would otherwise act as an interference
coating, hampering paint adhesion. After cleaning, pretreatments to remove corrosion
products can be applied.
One such brass pretreatment is bright dipping. This is done by immersing the
brass in an acidic solution. Bright dip solutions are available from electroplating
chemical suppliers. Suppliers of bright dips can be found at www.pfonline.com
on the Suppliers page and are listed on pages 342-343 in the 2000 Products Finishing
Directory.
Brass can also be pretreated by abrasive blasting. Suppliers of abrasive blasting
equipment and materials can be found at www.pfonline.com on the Suppliers
page and are listed on pages 309-314 of the PFD.
As I mentioned in a previous Painting Clinic, people who coat copper and brass
wire “pre-anneal” before coating. The wire is passed through a high-temperature
steam chamber with an inert gas atmosphere to exclude oxygen and eliminate any
explosion. The hot wire is then quenched before coating.
