Metal finishing Q&As since 1989
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Rusting of cast iron parts
Q. I work in an industry wherein cast pulleys & other CI castings are used. And with the climatic conditions in India, the parts get rusted even before the products are sent off for shipping. For prevention, practices like paint etc are done, but they are not effective & durable over a long period of time.
If anybody knows a solution to this problem like any additives or precautions during casting process, please come with the information.
Thanks,
petrol pumps - Mumbai, India
2006
A. Try 20 gm tannic acid [on eBay or Amazon]/15 gm phosphoric acid/1 lit water(or 800 ml water and 200 ml alcohol) solution-that is simple and cheap rust converter [on eBay or Amazon] (objects must be grease free). After treatment object must be oiled, waxed or clearcoated. Hope it helps and good luck!
Goran Budija- Cerovski vrh Croatia
2006
A. You may use rust converter [on eBay or Amazon] on the already rusted parts. This stops further rusting as all the available rust is converted to a complex polymer and no further rusting takes place.
SATYAJIT SHAH- Mumbai, Maharashtra, India
2006
Q. I am working on a radiant floor heating system, my question regards using cast iron pumps and water over time. The water they will be pumping is usually between 90 and 140 degrees, and they will operate a few times a day in the winter. They water is pulled out of a large reservoir. It is an open system in that it is not pressurized. So my question is, is there anything I can add to or do to the water to make it less apt to rust the pumps, or slow the rusting process? All the internals of the pumps will not rust, but the main case will. I have read a number of posts on the subject, but none seem to come to any real solution. They sell Stainless pumps, which would solve the problem, but they are 3x the price and I need about 10 of them. Any thoughts would be greatly appreciated. Thanks.
Richard Turner- rocky gap, Virginia, USA
December 13, 2015
December 2015
A. Hi Richard. Simple automotive anti-freeze will probably reduce the rusting, and keeping the water slightly alkaline rather than slightly acid will help. But people who do boiler servicing can probably recommend treatment chemicals that do better. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 15, 2015
A. The NYC water authority (DEP) adds a bit of sodium pyrophosphate to the tap water. This is to inhibit the dissolution of lead from solder joins in old pipes. Might help you as well.
I've also heard of glycerin being used as a heat transfer fluid.
Dave Wichern
Consultant - The Bronx, New York
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