Zincate Problem?

[JGray]

I have been plating steel with bright nickel and getting outstanding results. I recently expanded this process to plating some items I made from 6061 aluminum.

Dipping in the zincate as per instructions gives a "charcoal grey" coating to the aluminum. When I move to prepare the part for nickel plating, the SP degreaser results in a reaction with a moderate amount of small bubbles liberated from the part. Subsequent bright nickel plating results in a plate which peels right off. This result is indicative of inadequate cleaning, but I cannot find the problem since the zincated part's preparation is the same that I use for steel preparation which works fine.

I suspect the problem lies in the prep. of the part prior to zincating or perhaps the zincated part requires some prep. prior to nickel plating that I am not aware of. Any help will be greatly appreciated. Thx. J Gray

[fly]

You should rinse the part afte zincate then go straight to the flash copper or nickel.

[JGray]

Thanks Fly, I'll try that. A previous post from a year ago pretty much iterated the same. It also recommended flash copper prior to the nickel because the zinc would eventually contaminate the nickel bath. Would dummy plating the nickel bath remove the zinc contamination?

Thx. J Gray

[fxstcguy98]

I just plated some aluminum parts that were giving me fits. I found that you need 25 to 50% nitric as a prep.30 seconds in nitric, 30 seconds in the zincate, another 30 seconds in nitric, then 30 seconds in zincate then straight to flash copper live. Keep the power up a little for the first minute, then back it down to the correct level. The double zincating ensures a good grip with the flash.

[fly]

That is correct on what fxst98 said, but if you don't have the nitric acid then you might be able to get the parts to plate if you just zincate, rinse, and then go LIVE (connecting the neg. wire before part going into bath) in your flash copper, make sure you plate at low amps if you don't have the nitric acid, that is after you properly prep the parts.
Before I got the nitric I had the same problem with blisters but not as bad as you described.
But if you follow the steps that fxst98 posted then you will get a good finish every time without any questions, but I don't go into the nitric first, I go Zinc,rinse,nitric,rinse,Zinc,rinse, live in the flash... I do alot of sport Bikes and all the parts that are alum. come out perfect the first time...
If you get a cover off of a bike make sure that it is alum. cause some bikes have a magnesium part on them and the nitric will eat them up. So do a test before you put the part in the nitric, just drip a little nitric on the cover to see if it will react.. SO BE CAREFULL FXST98!!!!!!

[fly]

One thing I forgot to mention is the nitric acid can also be used to strip the nickle and copper off of just alum. parts, by just leaving them in the bath for about 15 to 20 min. But make sure its alum. first.....
You have to strip the chrome first if its chrome plated..

[JGray]

My thanks to both of you. I can obtain some nitric acid and will hopefully try plating the aluminum again tomorrow. It is really great to have access to knowledgeable people who are willing to help.

J Gray

[fly]

any time, let me know how it turns out.....

[eprigge]

Just out of curiousity, what is a good/economical source of nitric acid for this purpose?

[fxstcguy98]

The first place to look would be a local chemical supplier that sells small quantities. If you're not that lucky, do a google search for nitrc acid and be prepared to pay out the nose for small quantities and a hazmat shipping charge. I bought a 70% solution and diluted it because it was a cheaper route for me. Buy the cheapest one, you don't need the high quality lab grades.