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Masking for Electrostatic Powder Coated parts.

Masking for Electrostatic Powder Coated parts.

Masking for Electrostatic Powder Coated parts.

(OP)
We are currently having problems with masking Electrostatic Powder Coated parts.  

Hand masking with teflon tape is too expensive.  

We made plastic masks of a material recommended by the Coater but they melted in the 400 deg F bake.  

Then we made Stainless Steel masks but where the coating bridged between the part and the mask left an unacceptable serrated break line leaving exposed metal when the parts were assembled.  

The coating vendor then told us to put a .010 in. gap between the edges of the part and the mask because the coating would not bridge this gap.  This resuted in a build-up of coating in the gap and the need to scrape the excess off the area that is not supposed to be coated.  This is very time consuming and expensive also.

Does anyone know of a better means of masking parts for mass production or a better coating alternative for Ductile Iron which must be both durable and okay for food applications?

Thank you,

Bob

RE: Masking for Electrostatic Powder Coated parts.

What about using paper caps?  If they can be applied between pretreatment and coating, they are an option.  Paper burns at 451F.  Other products are available in silicone, vinyl and other materials from places that specialize in masking.  Since you have not described what you are trying to mask - threaded holes, studs, etc. - it is difficult to give a detailed answer to your dilemma.  

RE: Masking for Electrostatic Powder Coated parts.

(OP)
Thanks for your input.

We are masking round machined parts which need external surfaces powder coated, some with cross drilled tapped holes that need to be masked as well.  We have plugs for the tapped holes and are stacking the parts between masks to maximize the number of parts in a lot.  

I was mistaken about the bake temperature, the paint needs 400 deg F to cure but they heat it to 450 deg F to insure that the stack of parts has reached the required temp.  This would bring the paper to its flash point considering the tolerance of the oven.  

The teflon tape tended to cause a build-up of paint at the edge, as if the paint slid off the teflon and onto the part.  This also occured with the teflon plugs on the tapped holes.  

Right now we are trying to control the build-up to the edge of the non-painted surface and scraping it afterwards.

RE: Masking for Electrostatic Powder Coated parts.

Use Silicone Adhesive on Dead Soft 3 or 4 mil. aluminum foil.  Can also produce the foil with a MYLAR strip mask on top, or can laminating the Foil on Top of the mylar to build it up.  Typically Mylar Green Powder Coat mask is 350F film, 500F for the silicone adhesive.  Other products are plasma spray masking such as silicone impregnated or foil coated glass cloth tape.  These are very thick tapes 7 mil. to 50 mil. and can be double-layered.  I have sold many of these to the aerospace for HVOF masking of aircraft parts.

RE: Masking for Electrostatic Powder Coated parts.

Custom silicone paint masks made specifically for your part shape and dimensions are available from several companies. The masks will take 500F and are re-usable. They can also eliminate the bridging problem you are having and leave a clean paint line. If designed correctly they can decrease  handling (increasing line speed) and reduce rejects. These masks are used in high volume automotive applications all the time.

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