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Rusting Problem in Phosphated Parts

We are doing phosphating on ferrous parts. After Phosphating, when we take out phosphated part out of water tank after rinsing, some water drops remain on part. After some time these water forms rust on that part. Is there any chemical available, which can mixed with rinsing water, so that all the water leave part after rinsing, or do anybody have any other solution?

Anil Rajveer Sharmaa
- Faridabad, Haryana, India
2007

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First of three simultaneous responses -- 2007

Anil,

If you aren't already doing this, you should dry the parts after rinsing. I think allowing the parts to dry in the air will cause rust, as the phosphate will not protect the steel substrate from rusting in this situation. You may want to use a seal solution after phosphate (your chemical supplier can give you recommendations on this) as this will help. Heating the final rinse or seal will facilitate drying, and you may have to use forced air knives or a dryer.

Thomas Kemp

Thomas Kemp
- Erie, Pennsylvania, USA

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Second of three simultaneous responses --

I think that most people would use compressed air to blow the water off the part and to force dry it. You might try adding isopropyl alcohol ⇦this on eBay or Amazon [affil links] to the tank. It reduces the surface tension so more will run off, it will dry faster and the retained liquid will contain less water. Safety--Do not exceed an alcohol percentage that will burn. (also, it will cost more than water)

James Watts
- Navarre, Florida
2007

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Third of three simultaneous responses --

Phosphate coatings are not corrosion resistant so any water you leave on the part after processing will cause corrosion.
You need to dry the parts with a forced air line. You can go through a final chromate rinse if the specification allows it but you will still need to dry the parts immediately after rinsing.
You may also find that a hot water (60C) rinse may aid in the drying of the parts.
Supplementary treatments should be applied as soon as possible after phosphating so as to prevent any corrosion.

Brian Terry
Aerospace - Yeovil, Somerset, UK
2007

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You might talk to your chemical supplier about some kind of a surfactant, but the best thing to do is get the parts dry as quickly as possible, like putting them into an oven right after the last rinse or blowing as much water off as possible with compressed air.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2007

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Companies that sell phosphating chemistries usually have anti-rusting rinse aids & seals (in addition to the environmentally unfriendly hex. chromium type).
Guardian Anti-Corrosives Private Ltd. is a mfr. & supplier in India. Verify that any supplemental treatment is compatible with further processing (e.g., painting) & final use.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007

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Dear sir,
First, I need to know what type of phosphate you are using ( iron, zinc .....)? but anyway, you can try to use DI water rinse for last rinsing (pH 7 - 8), it is the cheaper way and environment friendly.

Jaff [surname deleted for privacy by Editor]
- Malaysia
2007