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Three Stage Phosphate System Design


Working on an engineering project to purchase a new iron phosphate system. We are investigating if a 3 stage process using a non-chrome sealer would be feasible. We phosphate compressors, 45% cast iron, 45% hot rolled steel, and 10% cold rolled steel. The predetermined engineering specification is 600 hours. We go into a liquid water based paint. My question involves if this sounds like a feasible system and also how should we be running the salt spray on these? The lab currently scribes in 1 spot for the 600 hour test and checks for loss of adgesion every 100 hours. Should we be pulling on the tape every 100 hours? Is that causing premature failures?

Theresa Fowler
- Huber Heights, Ohio


600 hours is a pretty tall order for a 3 stage system using water based paint and a non-chrome seal. If you were to be using a powdercoat, it would be a little easier. I think it might be do-able though, using the right parameters. I would also look at the corrosion test using a creepage measurement - scribe a line, and measure the corrosion creepage from that line until it makes it to the predetermined failure point.

Dan Brewer
chemical process supplier - Gurnee, Illinois

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