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topic 7316

Air Knifing Rinse Quality Impact On Iron Phosphatized HRS / CRS


I am curious on the actual surface substrate finish on a piece of hot or cold rolled steel that has been wand phosphatized with a low pH Pickling iron phosphatized product and then is air knifed off instead of rinsed off with a seal rinse. If a person does this phos wash at a low pH ( say 2.8-3.2 ) what is most likely the condition and quality of the supposed iron phosphate conversion coating ? I feel that even though the part is clean to the touch and minimal residue is picked up in a white rag check that the surface of the metal could be pretty acidic upon any humidity or moisture permeating the paint film. Could I be altering the surface "Charge" from cathodic or anodic etc. ? Any comments or observations on these 3 areas would be appreciated. Thanks in advance Brian, Sioux Falls

Brian Lamphron
- Sioux Falls, South Dakota , USA



You are right to be concerned. Failure to rinse off the surface with clean water will result in premature paint failure due to osmotic blistering. In air conditioned premises this is less likely to occur as humidity will be controlled.

If the chemical is injected into the lance then it should be possible to turn off the chemical and give a post rinse


Roger Bridger
- Croydon UK


Ditto. You have no choice but to rinse the part. So called no-rinse products contain rust inhibitors, but these are for in-process rust, not meant to be long-term or high quality.

Jeff Watson
Jeff Watson
- Pearland, Texas

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