Letter 37056

Nickel peeling problem 

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We are barrel plating millions of very small metal pieces monthly. The same semibright nickel baths are also used for coating larger components. Our problem is that occasionally the very outmost nickel layer is peeling of in tape test. Also in microscope studies we can see strong layering and sometimes even cracks parallel to the substrate. It looks like the problem only exists in plating specific shapes. The adhesion to the substrate is good though.
Does anybody know why this kind of phenomena can be seen? Inner stresses? Current cuts and passivation? Organic impurities? Barrel movement? Something else?
Please give me an idea how to proceed here. I am beginning to feel a little bit stupid.

Vesa Kankare
plating shop - Finland

You need to give more details. Pretreatment details, plating chemistry and parameters, type of arrangement and equipment used (barrel only or hang of larger parts).

Guillermo Marrufo
Monterrey, NL, Mexico

Firstly, what kind of material is it? pretreatment, activation of substrate is very important, but is not all.

How are obtained the pieces. Also this depends a lot.

Dan L. Rujan
- Arad, Romania

If appears you have nickel from nickel flaking. Sometimes the problem is easily fixed, sometimes it requires more investigative procedures. It appears the flaking is caused by something going wrong in the nickel bath. First thing look for something that has changed. I suspect a bipolar electrical condition, make-break contacts, overloaded barrels, defective conductors or buss rails, and don't forget to inspect the danglers inside the barrels.

Larry Brannock
- Cana, Virginia

Hi Vesa,
I think your barrel loses contact. So you must serve the connection in your barrel.

Anders Sundman     surface finishing engineer Sweden

Please concentrate on Barrel's motor speed, Activation of the parts, anti pit concentration, organic contamination, excess of brighteners/additives.

Shafiuddin A. Mohammed      metal coating shop - Dubai, UAE