Cleaning Primer Coat on Valve Stem 1

[Weko]

Hi all,

We ordered valves to the vendor. With painting specification of SP with Primer Inorganic Zinc DFT 75 micron.

The problem araise when the vendor did not paint the valve according to good engineering practice. They paint the valve stem also. So the valve becomes hard to operate.

Is there any suggestion how to remove the paint on the valve stem?

 

[TVP]

There are three basic methods for coating removal: media blasting, chemical removal, or thermal/burn-off processes. There is a wide variety of media used for blasting, such as plastic pellets, dry ice, sand, and various naturally derived items (corn cobs, rice hulls, walnut shells, etc.). Chemical processes may involve aggressive acids or bases, organic solvents, or molten salts. The thermal process is commonly used to remove organic paints (polyester-based powder coats, epoxy electrocoat, etc.) from steel parts by heating them to ~ 800 F where the organic layer decomposes. Here are a few references:

Stripping e-coat and powder coat

http://www.mileschemicalsolutions.com/images/Powder Coating Article,pc_20070901_0039.pdf

Organic Coating Removal

http://www.p2pays.org/ref/02/01048.pdf

Environmentally Safe and Effective Processes for Paint Removal

http://ftp.rta.nato.int/public//PubFullText/AGARD/LS/AGARD-LS-201///AGARD-LS-201.pdf

 

[Weko]

if we remove the paint, how about the surface of the stem? will it be smooth again? or becomes rough because it has been sand blated before the painting?

 

[TVP]

It depends on which process is used. I suggest you discuss this with some coating removal vendors in order to determine which method will work best for your application.

 

[TomDOT]

TVP: I would add a catchall "other mechanical means" for paint removal categories to cover scraping, sanding, grinding, scabbling, flapper-wheel, needlegun and all the other SP2/SP3/SP11 surface preparation methods. Some coatings can even be removed by "freeze it and hit it with a hammer" methods.