plating aluminum

[mickeytank]

i have been plating hard chrome for 24 years, just started in triple chrome as a side project, when i zincate a part then copper or nickel plate it comes out great, when i chrome it , it peels all the way to the bare aluminum. what gives? i have tried this many , many times, thanks for any help. you can e-mail me at .. mtankovich@comcast .net

[bhhodges]

it sounds to me like your nickel went passive and you need to use an acid salt " pickel" to reactivate the nickel prior to chrome plating.

bill

[dadkar2]

If it is peeling to the bare aluminum it sounds like you never had a good bond to the aluminum substrate in the first place.

It might be that the current was set too high during the chrome step, but this is less likely than a bad bond to the base metal. Sounds like you should re-evaluate the zincate process you're using.

Ken

[XK120DHC]

Bill;
I've seen and heard this term, "acid salts" a number of times,,
As a "I a fixin' to be a plater" for the past year (I've got the kits, I'm learning the chemistry and processes), I've done google searches, looked thru the Caswell manuals (I have V. 2, 7 & and read a lot of the posts on these forums.. But I can find no definition of exactly what "Acid Salt" is... Help!!

[jimcarry]

I think ken is right in saying that you probably do not have a good bond to start with.The section on Acid Pickles is on pages 34 through 36 of version 8 Plating Manual

[-ego-]

A few questions?

1. In the manual they show pickle #1, pickle #2, pickle #3 and Pickle #4. Which one is used to re-activate the nickel? Also, how long does it take for a nickel plated part to deactivate meaning that you have to re-activate using a pickle? I have had similar problems when black kroming nickel plated aluminum parts.

2. Also, if you dry shine the nickel plated part in a tumbler with walnut shells and rouge to enhance the shine of the nickel which takes a day or so, after degreasing should you re-activate the nickel with a pickel before proceding to plating.

3. Can you nickel plate over nickel plate?

I spoke to a company in California who decorative chrome plates our machined aluminum drum lugs. He told me that they etch, degrease, double zincate?, then double nickel plate, and then chrome, gold, black chrome, etc.

I wonder what the double zincate is all about and he also mentioned that the first nickel bath is not a bright nickel and the second was a bright nickel? It sounds like they are doing a triple chrome process but replaceing the copper with a layer of nickel.

[fxstcguy98]

1. I use pickle #3 for 10 to 20 seconds. If you come out of the nickle tank rinse in ROOM temp di water and go directly into the chrome tank, you should be fine. If it's out for more than a couple min. it will passivate (deactivate) or if you use hot water in will passivate.

2. definately

3. yes if it is activated prior to plating. But you can't plate over chrome plate, make sure that is stripped off first. However, I don't know the process for blackening chrome, is that like a dye on the chrome surface?

Zincate is used to plate alum parts, double zincate means they zincate it, strip it and zincate again (this ensures a good bond). Then they use a neutral nickle (no brighteners and additives) for a strike coat which gives a better bond than bright nickle and it's more ecconomical (you could also use cyanide or alkaline copper for a strike). Acid copper in triple chrome plating is used like bondo, if the part is smooth or you don't need the insulating qualities, copper can be skipped.

[-ego-]

Thanks for the tips...

How do you strip the zincate? in order to re-zincate?

Also, what exactly is a nuetral nickel. Is it like the nickel tank set up caswell sells and then not adding the brighteners? Would that work as a nuetral nickel?

[fxstcguy98]

To strip zincate, it's best to use nitric acid, but I use the pickle #3 and just keep a close eye on it, when it stops fizzing, wait a couple of seconds and take it out, rinse and zincate again.
Neutral nickle is a different formula than caswells bright nickle. Use caswells flash copper in place of the neutral nickle (I was just explaining what double nickle meant).

[-ego-]

1. What is the difference between the flash copper and neutral nickel?

2. Why would this plating company use a neutral nickel in replace of the copper?