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Surface Coating And Treatment Of Plastic Extrusion Screws

I want to know how to make plastic processing twin screws with hardened flights [maybe nitrided] and all the other surface triple chrome plated . I want to process cPVC pipes for which triple chrome plating of screw is must .

Deepak Poddar
plastic pipe extrusion - Bangalore, Karnataka, India
2004

CPVC contains chlorides and nickel is far more resistant to chloride attack than chrome. As a matter of fact chlorides are is used for stripping chrome. Flights can be hardened by welding or spray and fuse process using hard nickel alloys. Nitriding is not very resistant to chloride attack either.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

I agree with the previous post. But I have also used triple chrome plating with success for corrosion applications. Chrome normally does not work but by triple chrome plating the chrome becomes non porous and doesn't get undermined by the chloride gas.

Ron Anderson
Feed Screws and Barrel - Cocoa, Florida, USA
2004