Cheap alternatives to Chromate post-treatment
I'm a chemical engineering student at Oregon State University. I have a waste/cost minimization project on which I am currently working. Basically I'm working on post-treating a phosphate coated car body. I was wondering what the options are for corrosion resistant post-treatments. I'm currently using Chromate post treatment, and was wondering if there is anything cheaper out there?
Oregon State University - Corvallis, OR
There are a lot of post treatment which do not involve chromate post rinse. They are not cheaper by price but they are cheaper in waste treatment.
I suggest you will write to Henkel Surface Technology, they have some chrome post treatment replacements.
You can use the unique alternate metal surface preparation & pre-treatment process, by an environmentally safe, non-hazardous chemical, which will eliminate Chromate treatment before finishing (also, will eliminate any acid wash and/or phosphate treatment during surface preparation), giving a long term corrosion protection. It has Zero Waste Discharge and very cost effective, which you are also looking for and provides quality results. Ranjit Sen
- Huntsville, Alabama
We wouldn't ask or expect you to give away trade secrets, Mr. Sen, but this is a technical information service and it would be appropriate to generically identify at least what broad family of materials you are advocating, i.e., silicates, organo-metallics, organics, conversion coatings, etc. Can you identify any manufacturer using this on car bodies to eliminate acid washes and phosphates? Any literature quantifying 'long term corrosion resistance'? Thanks.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
To answer your question, how this alternate process does on car body and paint, we had test done on hot rolled sheet metal (same gauge as car body, but instead of cold rolled, we used hot rolled with mill scale). The metal was dipped in Picklex, to do the de-scaling & coating at the same time, then dried. We gave to an auto body paint shop to do the paint job, as an actual field test. The salt test passed 1540 hours, which is more than three times the car manufacturers requirement of 500 hours, on their factory paint job.
Also, lot of time the car body gets powder coated, in which case we used the same alternate process to powder coat the metal and passed 1500 hours of salt spray test.
A summary of all the tests on various finishing has been attached (attach 1).Ranjit Sen
- Huntsville, Alabama
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