Welding over Manganese Phosphate

[mridey]

One of our suppliers is having problems seal welding a valve body joint where the parts have been manganese phosphate coated. Base material is cast steel (WCB). Welds are not always so good, and don't seal.

I've read where welding over Mn-Phos is no big deal, and just the opposite. I'm inclined to have the coating removed first, but if that's not the problem I won't.

Suggestions?

 

[CoryPad]

Remove the coating, it can interfere with proper welding.

 

[metengr]

The coating must be removed.