49074

Brass plating peel off  

June 19, 2008

I am doing brass plating on zinc die cast (Zammak)and experience a problem that plating is peel off from the metal of base my process cycle is
chemical degreasing
electrolytic degreasing
dipping (acid)
copper cyanide
brass (cyanide base)
some time i am using only chemical degreasing but problem remains same....i am also trying to do direct brass after pretreatment but not resolve the problem

can any body solve this issue ?

Azhar Mahar
employee - Karachi

you can also use calcium oxide / calcium hydroxide to precipitate carbonates, but see that temperature doesnot raise too much which will lead to cyanide break down and carbonate buildup.
Good luck
Mukesh

Panjala Mukesh      fashion jewelry mfgr. Hyderabad, India

Dear sir in your process flow you are mentioned acid dip what is the acid you are using. If you are using any strong acid surface over etched and form black smut on the surfce leads to the problem. use dilute mild acid for surface activation andmaintain bath parameters both copper and brass

Suresh Reddy
- Bangalore, India

As you ask about acid dipping, it is actually dilute sulphuric acid for neutralization of material after alkaline degreasing.

Azhar Mahar
- Karachi

Azhar, I think you have to concentrate on the base metal too. Since Zammak is an alloy of Zinc with alluminium, manganese, cadmium, etc., there are the chances of having blister\peeloff due to low conductivity. check out for the conductivity of your brass electrolyte. And even carry our Quenching test on your base metal, say, after plating copper cyanide plate metal otherthan brass. I think, u have to check even temperature, anode passivation, carbonate concentration, or contamination of DM water with chlorides.
All the Best

Shafiuddin A. Mohammed      metal coating shop - Dubai, UAE

o yes your base metal must be porous ,thats why plating is peeling off. try some other metals and see the plating still peeling off or not?

Aftab Jahangir    chemist Karachi, Pakistan