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Surface Preparation for Phosphatization of Carbon Steel

2002

I work in the coatings field at a major Shipbuilding facility. However, Chemical Conversion Coatings and Powdercoating are not my area of expertise. We have started up a rather large, (in my opinion) Powdercoating line, and I am in need of some basic information. The questions I have, concerns preparation of carbon steel using cold waterborn phosphatizing solution prior to Powdercoating:

1.What is the recommended surface cleaning grade?
2.Does the existence of mil scale in any amount affect the formation and performance of the protective phosphate coating?
3. Does the existence of iron oxide on the steel surface, in visible amounts affect the formation and performance of the protective phosphate coating?
4. Since we run the parts through a Centrifugal Blast unit, what would be the minimal SSPC equivalent cleanliness grade to achieve prior to Phosphatizing?
5. What is your opinion on overcoating phosphate films using functional epoxy powders at film thicknesses of 4 to 10 mils for saltwater emersion service?

Thank You for any information you can provide.

Regards,

Charles B. Harvilicz
- Newport News, Virginia

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2002

Hi Charles,

I can answer some of your questions.

1.What is the recommended surface cleaning grade?
I don't know what "recommended surface cleaning grade" means.

2.Does the existence of mil scale in any amount affect the formation and performance of the protective phosphate coating?

3. Does the existence of iron oxide on the steel surface, in visible amounts affect the formation and performance of the protective phosphate coating?
In order to deposit any kind of conversion coating on a metal surface, the surface has to be free of contaminants. These include grease, oil, smut, and corrosion products.

4. Since we run the parts through a Centrifugal Blast unit, what would be the minimal SSPC equivalent cleanliness grade to achieve prior to Phosphatizing?
I don't have an answer for this question.

5. What is your opinion on overcoating phosphate films using functional epoxy powders at film thicknesses of 4 to 10 mils for saltwater emersion service?
This question is difficult to answer. Will the metal surface be treated with an iron phosphate or zinc phosphate? The latter is much more corrosion resistant. What kind of performance criteria need to be met for this type of environment?

George Gorecki
- Naperville, Illinois

Uniform Industrial Process Instruction (UIPI) 0631-901A may hold some answers for this query regarding surface profile, SSPC prep, contamination, etc. A copy of this document has been forwarded to this company.

Ken Scandell
Naval Sea Systems Command - Virginia
2002

Please inform me where to find sections of the Uniform Industrial Process Instruction (UIPI). I have been assigned to update a military publication that cites a section of this publication as a reference, and I must know the latest revision of that section (or possibly of the whole Instruction); the date; whether still valid; etc.

MILTON S LINDNER
- Washington DC
2004

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October 3, 2008

Ken Scandell,

Could you forward this UIPI to me as well?

We are a long time manufacturer of doors and formed parts for the navy and we need this to properly certify our materials.

Thank you

Steve Henderson
- El Monte, Calif, USA

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October 21, 2008

Hi, Steve. We've now put the date on Ken's posting and you can se that it was some years ago. He's probably not checking this page frequently if at all, so you may want to try to phone him.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey