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Iron Phosphate over Cast Iron?

I am interested in knowing whether TT-C-490 [affil link or DLA] , Method Type II (iron phosphate) can be applied over cast ductile iron without any problems. I know that it can be applied over forged steel, but was wondering about the cast iron. The chemistry of the cast iron conforms to ASTM A536 [affil link] , Grade 60-40-18. Also, are there any manufacturers that have baths suitable for treating a pipe that is approximately 5-ft long? Thanks, Marc

Marc Pepi
US Army Research Lab - Aberdeen Proving Ground, Maryland, USA

Iron Phosphate coatings will form on cast-iron with no problem, getting a good coating without flash rust is a little more of a trick. Many shops can process a five foot piece of pipe, some can even do it in large quantities on a conveyorized line. Assuming your part is to be coated after phosphating, you will most likely need a good rust inhibiting final rinse, and a fast dry cycle to get the water off before it can pull out too much iron.

Jeff Watson
Jeff Watson
- Pearland, Texas

Q. I am having trouble with phosphating of cast iron; please suggest the compositions of chemicals and the process for optimal results.

Kiran Kumar
- Delhi, India
March 2, 2012

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