jonnyclf999

Topic: Chrome plating blistering!

I am currently having some problems with stainless steel trims which have been chrome plated. once chromed, they are welded to un-chromed stainless steel pipes. The problem is that on many occasions the chrome will blister and so the trim has to be scrapped. I understand that the most probable cause for this is the actual chrome plating process which may not be adequate but i am wondering if anyone knows of any ways in which to solve this problem without changing the chroming process. The blistering does not occur everytime or when it does occur it may not be at the same stage of the assembly. It can occur immediately after welding of can occur after final assembly whicch is much later on in the process.Our initial ideas were that the heat transfer from the weld is causing the blistering further down the trim and so have considered using cold front heat blocking paste or storing the trims in water between processes to restrict this heat transfer.

Any help or ideas on this would be appreciated

Jon

DustinGebhardt

Re: Chrome plating blistering!

As you have already stated, the most likely SOURCE of the problem is in the plating itself.  Are you looking to fix the root cause of the problem or only address the symptoms?  In any case, here are my suggestions (I am assuming this is for decorative purposes and uses an underlying nickel layer):


1) Stainless steel is difficult to plate.  Pretreatment and activation are extremely critical.  A good degreaser is a must.  Make sure the parts shoudl no evidence of water break after acid activation.  The acid activator must be strong and fresh.  Cathodic activation is also a good idea, as are using other ingredients commonly found in a good acid salt additive.

2)  A good nickel strike is very important.  Going in with reverse current before you apply the nickel deposit can also help adhesion.

3) To minimize the effects of bimetallic expansion and contraction, you want to minimize the amount of nickel (and chrome) you put on the part.  A compressively stressed (as opposed to tensile) nickel deposit will tend to help adhesion, so minimize the secondary brighteners and keep the carrier up.

4) I have also heard of people stress relieving the parts after plating to slowly release the stress rather than hit the part all at once with the huge heat load of a weld.  I have never seen this personally.

-Dustin Gebhardt,
CEF
Plating Engineer
Danaher Tool Group
Gastonia, NC

jonnyclf999

Re: Chrome plating blistering!

Thanks for the reply.

As you stated the actual chrome process is outsourced so we have no control over it. I believe we are attempting to address the problem at this stage but until it is resolved i was trying to reduce the after effects such as blistering and bubbling.

The quality of the finished trims is critical and so any slight bubbles, marks or blisters will result in rejections.

I have struggled to find any information regarding welding chrome plating in general.

Any more information that you may have regarding this issue would be greatly appreciated

Jon