Welcome to FSM, Steve. You may want ot check the A/C forum. Tons of aircraft stuff there.
Good luck.
As for the zinc chromate:
Zinc Chromate is a priming paint for metals used to protect the metal surface from elements that causes reaction leading to rust and to enhance the bond of the final paint coats. Nowadays, it is still used in the steel industry and usually comes in bright yellow and grey colors. Previously however, I read that it is in yellow greenish or bluish colors but I haven't see such colors yet.