Serious Education ... plus the most fun you can have in metal finishing.
Bitumous paint specs
I need to find the specs for bituminous paint that would be used to isolate steel and aluminum and which will prevent galvanic reaction between the two. ThanksMarcus Merritt
Signage designer - Atlanta, Georgia
First of two simultaneous responses -- (2007)
Go to the Pittsburgh Paint Store and ask the clerk for the specs on Pittsburgh "Kold Kat Epoxy". He will have never heard of it, but he can find out for you.
Robert H Probert Technical Services
Garner, North Carolina
Second of two simultaneous responses -- (2007)
Some bituminous paints suitable for separating aluminum from dissimilar materials:
TT-C-494B COATING COMPOUND, BITUMINOUS, SOLVENT TYPE ACID-RESISTANT (canceled without replacement, 2001).
MIL-P-6883A PAINT, BLENDED-TYPE, COAL-TAR-PITCH BASE, BITUMINOUS (canceled in 1964, but still sometimes specified).
ASTM D1187, 'Standard Specification for Asphalt-Base Emulsions for Use as Protective Coatings for Metal.'
SSPC-Paint 12, Cold-Applied Asphalt Mastic (Extra Thick Film) [Society for Protective Coatings].
CGSB Specification 31-GP-3M, Alkali-resistant bituminous paint [Canadian specification].
Also, AASHTO Specification M-190 Type A [Type A = Fully Coated] is a requirement for bituminous coating, but I haven't details. American Association of State Highway and Transportation Officials.
Bituminous coatings are commonly used to protect aluminum from direct contact with fresh concrete and porous masonry. Aluminum to be embedded in concrete shall be painted with one coat of TT-P-645B zinc-molybdate primer or bituminous paint. Allow to dry completely before placing concrete.
For use with steel, both the aluminum and steel can be primered with "TT-P-645B, then top-coated with varnish containing 2 pounds of aluminum pigment per gallon. Varnish shall conform to Federal Specification TT-V-81G, Type II. Aluminum paste pigment shall conform to ASTM D 962, Type 2, Class B."
"Steel surfaces to be placed in contact with uncoated aluminum shall be painted with one coat of zinc-molybdate, alkyd type primer in accordance with Federal Specification TT-P-645B, followed by two coats of paint consisting of two pounds of aluminum paste pigment per gallon of varnish. Aluminum paste pigment shall conform to ASTM D 962, Type 2, Class B. Varnish shall conform to Federal Specification TT-V-81G, Type II."
Primer & topcoat specifications:
TT-P-645B PRIMER, PAINT, ZINC-MOLYBDATE, ALKYD TYPE.
TT-V-81G VARNISH, MIXING, FOR ALUMINUM PAINT (superseded in 1996 by A-A-1632).
A-A-1632 VARNISH, ASPHALT (canceled, 2000).
ASTM D962-81(2003) Standard Specification for Aluminum Powder and Paste Pigments for Paints
"Surfaces of stainless steel, aluminized steel, hot-dip zinc-coated steel, or electrogalvanized steel to be placed in contact with aluminum shall not be painted unless otherwise indicated in the contract documents."
Quoted information from the Hawaii DOT specifications on the use of aluminum:
Most state highway departments have similar regulations concerning aluminum in contact with dissimilar materials.
- Goleta, California
Finishing.com honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
which the finishing world continues to benefit from.