Metal finishing Q&As since 1989

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Crevices and powder coating

Sir we are using cross members in our chassis(buses and trucks)CM is made of HR sheet in that lot of crevices are there.so during pre treatment chemical stay over there and during powder coating powder not goes inside..so is there any solution like sealant or waxing after final painting or before painting(remember)after powder applicatiot CM goes in oven for drying 210c for 20 minutes.....

ASHISH SHUKLA
Ashok Leyland - Chenai, India
2006

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2006

Dear Ashish,
You are using sealants and adhesives in your paint and body shop. One such supplier is Henkel Teroson India Ltd. They have range of sealants which can serve your purpose. You can call them and show the application and they will provide you with proper product.
Hope it will solve your problem.

Kulkarni Mangesh
- Pune, Maharashtra

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2006

Dear Sirs,
Although you do not indicate the type of pre-treatment we can assume that it would be a zinc phosphate. As any liquid (even the rinse water) will find its way into the cavities we would suggest that an alternative approach should be investigated and as the inner and outer surfaces require protection from the environment the following coating system is put forward for your consideration.

a)Coat all outer surfaces in a waterborne anti corrosive primer. Allowed to air-dry for about 20 mins.
b)Apply minimum of 70 microns of Epoxy Black powder over the primer and then bake to the powder supplier's recommendations.
To prevent any corrosion taking place on the hidden inner walls of the chassis we recommend:
c)Apply by air assisted spray or dipping method a wax treatment.
Any surplus wax straying onto the outer surface can be ignored.

Terry Hickling
Birmingham, United Kingdom