Letter 2032

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A client of mine does zinc phosphatizing. Some percentage of the incoming work (5 to 15 percent) is rusty and cannot go directly into his exisiting system. The question has come up of whether we can do in-line acid derusting in a new line. In other words, we would want to do alkaline cleaning, rinsing, acid derusting, rinsing, and then phosphatizing.

Does anybody use a derusting acid in a spray phosphatizing line? In a dip line I would use hydrochloric acid; should be spray hydrochloric acid or is there a better solution like dry acid salts? Should this compartment and its walls be PVC instead of metal?

I'd like to hear any opinions, but especially from someone who is doing it, or who did it and abandoned it.

Thanks!

 
Ted Mooney
finishing.com Inc. - Brick, NJ

Ted:

We have just a few customers who do spray pickling. We have had success with some proprietary products, no of which are muriatic, which I would recommend staying away from. The problem is that the amounts of rusting can vary and you must build the tank (Concentration and Temperature) to take on the worst case senario. This is not inexpensive.

It can be done though. Have you looked at treating the rust problem off line before the parts go to the washer? I assume so and that you found it to be difficult. Let me ask another question. Is the rusting due to a supplier problem or is it a storage problem at the customer.

The problem could be that the rust preventative put on at the steel supplier is not good enough to last long enough before your customer uses up the parts. Or it could be that the customer is storing parts too long before they are washed. Third, I would look for an atmopspheric storage problem in the parts warehouse. Examples of problems would be an acidic atmosphere, or outside storage, or storage in a very humid warehouse, or inappropriate packaging.

Let me know if I can help with product recommendations or in any other way.

Craig A. Burkart Nalco Company - Naperville, IL

Thanks, Craig. I believe that you are right that the rusty parts should be pre-treated offline. One good reason is so that the cost of allowing the parts to rust remains tangible instead of becoming hidden; and the economic incentive is retained. I appreciate your help.

 
Ted Mooney
finishing.com Inc. - Brick, NJ

Ted,

I have worked with several companies investigating spray pickling and none of them decided to implement the process. The problems include Time (length of zone), equipment materials, and surrounding environment.

I certianly do not recommend HCl in a spray process. If necessary, be sure to have it properly ventilated to protect your surrounding equipment and structure.

In short, look for an alternative.

Edward Koneczny
- Birmingham, Michigan

Dear Ted,

Itis interesting to note your problem of acidic spray derusting in spray phosphating line. With our long experience of over 30 years in studying and developing tailor-made products for the metalworking and metal-treatment lines, we are quite confident that our TECHPICK 917,which is an organic acid based derusting chemical can be effectively used for your requirement.It can be sprayed at 50 to 60 degree celsius at a concentration of 20 to 25 % in water.The product does not require any special effluent treatment except perhaps neutralisation with soda ash or caustic soda. Should you be interested, pl. feel free to write to me with more details or any queries that you may have. Best regards,

V.S.RAMANATHAN
- HYDERABAD INDIA

Dear, Sir I am mechanical engineer in engineering & Construction Co.,). We want to revamping our pickling line(Continuous carbon steel) . Thickness : 1.2 ~ 5.0mm, Width : 760 ~ 1650mm, Pickling Solution : HCL(18%). . pickling Speed : 110mpm , Capacity : 500,000Ton/Year(24Hour/1day). We will change the present tank(shallow type) to turbulent type after revamping. So, We need your heat exchanger & pipe(in HCL acid solution) and fitting,valve. Above all, we hope to make a pickling tank which is made PP(polypropylene) and fume scrubber,Pipe, etc. Please send me your company's experience project about remove acid fume scrubber in continuous pickling line and your company information.

Teag Young Park
- kyung-do,791-052,Korea

Dear Sirs,

I need some information. I have a pice of mettel and I wish to make it rust within 1-2 days. What kind of materials should I buy to make the meetel look rust ? what should I do to get rid from the rust after a week?

Zvika Lifschitz
- Tel Aviv , Israel

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