Abstract
After extensive research and development a method for passivation of electroplated zinc has been optimised to provide the best corrosion resistance. This optimisation has lead to two different treatments both based on mo-lybdate and phosphate (from this point forward referred to as MolyPhos). The treatments are within the same concentration region, and they have a mutual pat-ent pending.
Although some tests still need to be conducted, the following aspects are clear at the present time:
The general appearance of the passivated zinc surface is very similar to a standard yellow chromate treatment.
There is no known environmental or health risk involved using the treatments mentioned above. All components used in the baths are non toxic compared to Cr(VI).
Alloy coatings such as zinc/nickel, zinc/cobalt, zinc/tin and all types of pure zinc coating (from cyanide, acidic or alkaline baths) have been treated successfully.
The corrosion resistance against white rust on zinc and zinc alloys is just as good as that of yellow chromate, although the result de-pends on the corrosion test method as well as on the nature of the zinc substrate pas-sivated.
The passivation procedure is simply a dip for approxi-mately 2 minutes, in any one of the baths, at 60¢XC. Some movement of the submerged samples, or stirring with air-bubbles, should be applied, just as a thorough rinse of the zinc surface immediately before the pas-sivation is extremely important.
| Original language | English |
|---|---|
| Title of host publication | Symposium on the Search for Environmentally "Safer" Deposition Processes for Electronics |
| Publication date | 1993 |
| Publication status | Published - 1993 |
