plating, anodizing, & finishing Q&As since 1989
Racking for passivation of stainless steel
We are investigating alternatives to racking for passivation of precision machined product (small...1/2" to 12").
The issues are; damage caused by titanium racks (or baskets), and the effective cleaning at the contact area (a possible cause of flash attack... sorry to bring that one up).
We have not been able to find much information on product designed specifically for this purpose... we use some polly baskets, but the precision machined parts are damaged easily... we have some ideas on custom made items(polly holders, partitioned baskets, etc), but we hope to contact a vendor with a line of products that specifically address this issue.
Thanks for your help.
metal finishing - Toronto, Ontario
While titanium racks are really nice, we quit using them and went to SS. Where possible, we even used the same SS as the part. Since we built them ourselves, the biggest problem was keeping them separated.
Since you are an aerospace company, my guess is that it is the modified 410 that is giving you the grief. There are a couple of really good letters on that subject at this site.
For parts that are giving you grief, I would look at carefully putting them in a SS basket or a poly basket with lots of large holes. (Be sure to hang the basket with plastic so there is no source of dissimilar metal galvanic action) and let them soak for hours, overnight is fine, in the caustic cleaner. Obviously, start with a small sample and gradually let it get bigger. After a long soak rinse carefully and rack.
Tilton [Fairfield, NJ] and ARC are two companies that come to mind for racks if you chose to outsource.
The racks with "acorn" removable tips that can be made of virtually any stainless should be great for your operation. Cost is a relative thing. to a tiny shop with access to a TIG torch and home plastisol, in house, after hours by the managers was the only option. Not knowing the size, shape, weight and holes, and etc of your parts as well as tank size, specific racks can not be talked about.
- Navarre, Florida
Since you are just doing passivation you really don't need any current carrying capability in your racks. We have racks with plastisol coated tips that do not scratch or frost the contact point. It's also easier to dry the parts without spotting when they are on a rack because of the nesting of the parts in the spin basket. Most rack manufacturers will be able to build you what you need.
Mabank, Texas USA
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