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Pickling and Passivating Structural Steel

2007

I am currently working on a large structural steel roof structure, which will be used to cover a fermentation tank, releasing corrosive gasses. This structure will consist of 4 trusses, with a roof sheeting connected to the bottom chord of the trusses, the sheeting would be GRP profile sheeting, to resist the gasses, and I thought that 3CR12 grade steel would be the best solution for a anti-corrosive metal, but this limits the sections that are available in South Africa (where I am from).

I heard of the term "Pickle & Passivate", and found some info on this procedure, but all the info I could get, referred to treating Stainless Steel.

Is it possible to use this treatment on normal grade 350W Structural Steel? or is there maybe another procedure that can be used to treat steel in order to make it Anti-Corrosive?

Christian Vorster
Structural Detailer - Nelspruit, South Africa

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Passivation does not apply to steel, Christian, as it does not contain significant chromium and the process is designed to passivate the chrome. A phosphate pretreatment followed by electropaint priming followed by epoxy powdercoating should be reasonably corrosion resistant.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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First of two simultaneous responses --

Christian, choice of suitable cladding material is greatly influenced by the nature of the gasses.

Your Southern Africa Stainless Steel Development Association is an excellent organisation which also puts out accurate and clearly-written literature on all aspects of stainless steels. It will have more than enough expertise to guide you.

The latest contact details that I have for the association is PO Box 4479, Rivonia 2128, telephone (011) 803 5610, fax (011) 803 2011, email sassda@pop.onwa.co.za

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
2007

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Second of two simultaneous responses --

Phosphating is the best suitable option,

But since your structures could not be dipped, you shall use brush type phosphating available in the Indian market.

For finishing, You go for 2 pack Epoxy paint which has Polyamide hardner with it. you can see that your results are excellent,

But I suggest you go for maintenance every 8-9 months with one coat of paint.

yours truly

O.Shankar

Shankar O. Khandelwal
- Coimbatore, Tamilnadu, INDIA
2007