Summary for flash rust phosphate spray Discussion
Flash rust after phosphate pressure wash is the central issue in this thread. Ron Isles asks whether a no-rinse phosphate degreasing and cleaning system can work in a pressure-washer setup without rusting before powder coating. George Gorecki explains that flash rust is a known problem when applying iron phosphate by spray wand and says a freshly phosphated surface can corrode easily, though he cannot judge the exact formulation of Ron’s Oakite/Chemetall Gardobond A 4961 product. Roger Bridger notes that the product is only optionally non-rinse and suggests a monoethanolamine-based cleaner for rust protection and overpaintability, adding that water quality and ionic content affect performance. Dan Martelli says high-pressure spray systems can be challenging and mentions an upcoming system with separate phosphate, rinse, and sealer stages. A later anonymous reply emphasizes that temperature and concentration are key and recommends test panels.
Q. Our company utilizes a Pressure Island spray system for degreasing tubular and sheet steel parts in preparation for powder coating. We have a problem with rust forming once the parts are dry and before we can powder coat them. The time interval is brief. We are using a no rinse system from Oakite [Chemetall]. The description is “Gardobond A 4961”. We monitor the ph level, concentration of solution and temperature closely. Yet, we are getting rust. My question is: Is there a no rinse phosphate degreasing and cleaning system out there that will work with a pressure washer and not rust?
Ron Isles
reproductions – La Mirada, California, USA
2002
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A. Hi Ron,
Flash rust is a troublesome problem when applying an iron phosphate by spray wand. Given the right conditions, a surface that has just been phosphated can corrode quite easily.
Normally, the phosphating product will be formulated to prevent the formation of flash rust. It’s not possible in this forum to know how your current product is formulated.
George Gorecki
– Naperville, Illinois
A. Ron,
I notice that this product is “optionally” non-rinse. I think you would be better to use a monoethanolamine based cleaner which would offer some rust protection and overpaintability. Pint performance of any process will be governed by water quality and the ionic content of the process.
Roger Bridger
– Croydon, UK
A. I agree that flash rust and high pressure spray systems can be a challenge in certain circumstances. FYI there is a high pressure system that will be hitting the market shortly that will have separate stages for phosphate, rinse, and sealer which can help solve your problem.
Dan Martelli
– Menlo Park, California, USA
2004
A. It is my understanding is temp and concentration is key. use test panels to check, they should turn grey, dark grey and look dull. 140 °C for temp, at 7 to 14%. This will survive 1000+ hrs salt spray, pass all scab test.
Haenlien
– Michigan
August 11, 2025
This is a meeting place for camaraderie & sharing, not a free consultancy. So some readers don’t engage with anonymous posters.