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Alodine 1200 over silver plate

2002

I have an aluminium assy with areas of selective silver plate. After various opps, such as soldering, the aluminium section is Alodined (1200). At the moment the assy is locally dipped in the Alodine bath. My questions are as follows.

a. Would the Alodine adversely effect the silver plate if the part were fully immersed as the Alodine is not the correct type of chromate conversion for silver ?

b. Would the resulting finish on the silver plate aid paint adhesion and possibly "do away" with the requirement for an etch primer on painting. I am informed that the etch primer is currently used on this part due to the silver plated sections.

Please note - The cosmetic finish of the Alodine on the silver is un important on un painted areas. The silver plate is 10µ min silver over 8µ min nickel (25µ max).

Richard Mosley
- UK

All of the aluminum chromate proprietary products ALSO leave a protective and paintable film on silver.

One vendor uses the same compound under two different trade names, one for aluminum, the other for silver, but it is the same compound.

In the 1960's when General Electric participated in the various space programs in Syracuse, Huntsville, and Daytona Beach, they had a specification calling for a certain proprietary chromate for silver, again, which was the exact same compound for aluminum under another name.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003