| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Surface Pitting
Can you give any advise on the problem of surface pitting of aluminium 6082 plated electroless nickel?
Rob Dummer- Mansfield, Notts, UK
2003
Rob,
Somewhere to begin: First you have to find out if pits come from the substrate or are only contained in the plated layer. For this, you can slowly sand or lap a coupon until the first trace of substrate metal shows. If the pores are gone then it's you plating process or chemistry. If they are still there, it can be a poor base metal or the pretreatment prior to plating that is attacking it.
Monterrey, NL, Mexico
2003
Pitting in electroless nickel deposits on aluminum is most often caused by the basis material. To minimize pitting, do not caustic etch, Use mild acids after cleaning (e.g., 5% phosphoric acid) double zincate using either nitric acid 50-60% by vol, or 5% sulfuric acid with hydrogen peroxide or sodium persulphate. Over etching of aluminum alloys creates pits by dissolving either the alloying constituents or causing the aluminum to dissolve around the alloy materials by electrochemical corrosion.
Also, organic contamination of the electroless nickel may cause pitting, along with particle inclusions, bacterial mold, etc. Generally though, EN solutions do not pit unless badly contaminated.
Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics"
and "Plating ABS Plastics" eBay or AbeBooks affil links])
2003
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.