| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Powder Coating over Zinc/Yellow
I have a new customer that makes racks similar to oven racks. They want them plated zinc/yellow. Then they powder coat them. The problem is they started running a test for adhesion by hanging the parts and hitting them with a hammer . It would not stay on. The former supplier ran an Alkaline bath we run a chloride bath. I know chromate bites much better on Alkaline than chloride. What I need to know is is there anything we can do to fix this? It's a big job and we really need it. We are very small and close to laying people off.
Any help would be greatly appreciated. THANKS
Andy Smithmetal finishing shop - Greeneville, Tennessee
2001
I believe you are right that alkaline zinc offers better chromate receptivity than acid zinc. (Dear readers: re-read that sentence and you are guaranteed to get at least one answer right in the "Test Your Plating IQ" column in this month's Plating & Surface Finishing magazine).
But I find it hard to believe that this difference alone would account for the powder coating just literally falling off. Are you careful to not expose it to more than 140 °F until fully cured?
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
2001
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.