CF8M (Cast 316 stainless) is easily electropolished to increase service life
Wednesday, May 5, 2010 at 12:35PM

CF8M, CF-8M, or cast 316 stainless steel sand castings or investment castings are used extensively to fabricate small to giant ball valves, gate valves, check valves, all the way up to very large complex pieces costing $10,000+

During the manufacturing process abrasive blasting is commonly used to finish the piece. The best material used on stainless is garnet and to keep stainless' corrosion resistance properties garnet is mandatory due to its inert, non-magnetic properties. If steel, sand or contaminated media is used it will be only a matter of time before rusting and subsequent part failure is observed (see picture below).

Sometimes it is not known how the surface of a CF8M supplied part has been finished or subsequently treated to restore stainless' corrosion resistance to meet or exceed specification. All to often the part is commissioned in use sometimes in very complex assemblies in this inferior state. If the part fails, then subsequent repair/replacement, and corrosion processing the piece in situ is a lot more difficult.

Pickling/passivation, or electropolishing will completely restore a "contaminated" surface of CF-8M back to meet and exceed specifications by removing all corrosion and regenerating the passive layer. In the picture below had this 10" valve assembly been pickled/passivated or electropolished, failure would not have occurred. The contaminated external surface can be processed in-situ however the internal surface is another story...

Failed 10" valve assembled between pickled/passivated piping. Had this valve been corrosion processed it would not have failed. Failure was due to shot blasting the valve with contaminated media.Electropolished used CF8M ball valve looks brand new!. This is what the failed 10" valve above would still look like had it been electropolished. 

Article originally appeared on electropolishing (
See website for complete article licensing information.