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Brown staining on electroless nickel plating




We are experiencing a problem with brown staining/ tarnishing appearing a few hours later on radio components that we are electroless nickel plating . The components are machined from solid aluminium billets and are electroless coated for one hour using a high phosphorous solution. After plating they are rinsed in de - ionised water and then blown with compressed air to clear any blind holes , corners, etc.Does anyone have any advise for us ? We cannot use any de - watering or oil based coatings as some components are then powder coated afterwards .

MARK WRIGHT
electroplating shop - DURBAN, KZN, SOUTH AFRICA
2006


The problem described comes from the bath constituents, contaminants and maintenance schedule, perhaps combined with transfer times, rinse pH and temperature. When plating Al, zinc is a common source of contamination which dissolves from the zincate layer. If you are using a proprietary chemistry ask your vendor. With home brew baths it's all guess and try.

Guillermo Marrufo
Monterrey, NL, Mexico
2006



2006

Your staining is most likely due to contaminates and rinse water. The addition of another rinse after plating containing approx. 5% chromic acid at about 40C will probably help eliminate staining and should not effect subsequent organic coatings.

Ron Duncan
Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.





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