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Pickling & Finishing Stainless Steel 409

02/28/2006 8:36 AM

Vijay Kumar writes:
I am facing problem in pickling and finishing of stainless steel 409 sheets and their welding joints.

Please suggest how I can finish the material by using some chemicals, but not using mechanical finishing. Also, if possible, please provide the composition of all the suggested chemicals so that I can perform the operation well, and cut down on the overall finishing time.

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#1

finishing ss 409

03/01/2006 8:18 AM

I work for a company that routinely polishes 300 series stainless steel with chemicals and electricity. (electro-polish). It may be possible to do 400 series, although we have never tried it. A cutlery company in the area has tried it with poor results, but they do not routinely electro-polish, so the technique they used is in question. The solution is a mix of sulfuric and phosphoric acids, and the current is low vlotage DC. Each steel type has a prefered mix ratio. We use from a 30% sulfuric to a 60% sulfuric mix depending on the material and the type of polishing we are doing. This can be done in a tank with copper electrodes or by manually with a copper wand. If I could get a sample, I might be able to polish this.

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#2

Pickling and Finishing?

03/01/2006 9:27 AM

Pickling and Finishing? What is the desired result, polishing for brightness, or passivation to remove surface iron and iron oxides? When I worked for a company that produced industrial heating panels we routinely us citric acid passivation, to remove surface rust (yes, "stainless" steel will rust, slightly, especially 409) and to prepare the surface for spraying on a black emissivity coating.

Here is a link to a good article on citric acid for passivation and compares it to "standard" nitric acid passivation:

http://www.pfonline.com/articles/059905.html

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Guru

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#4
In reply to #2

Re:Pickling and Finishing?

03/01/2006 10:34 PM

Very true, stainless steels exhibit varying degrees of corrosion resistance but are NOT "rust-proof". Do a Google or Ask Jeeves search on welding stainless and you will find a wide variety of links on welding, and finishing articles for review. Stainless steel can be very sensitive to welding and finishing techniques, and if subjected to iron impurities can show rust quickly.

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Participant

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#3

surfacing 409SS

03/01/2006 10:28 AM

Try Iron-6 (ferrate), easy to mix to your desided strength from a dry vacuum packed container right in your lab.

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#5

Stainless Pickles and Polishing

03/07/2006 2:24 PM

Global Stainless Technology provides electropolishing equipment for finishing stainless (see www.globalstainlesstech.com/GST_BHM_Article_9-27-9 9.PDF ). This might provide an alternative to acid pickles, which are hazardous to use and may cause environmental concerns. Typically, nitric and hydrofluoric acid solutions are used to pickle stainless steel. Henkel Aerospace sells an acid fluoride based additive that is added to nitric acid to create a stainless pickle (see www.aerospace.henkel.com/Images/Datasheet_PDF/hst_ turconitradd.pdf ). Avesta Finishing Chemicals (see www.avestafinishing.com/ )sells a variety of pickles and cleaners for stainless steels; some even in gel or paste form. ASTM has standards for stainless pickling procedures, which you may want to reference - ASTM A380 Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems. If you are in a pickle on what to do, then you might want to attend one of Avesta's training workshops on pickling or contact them about their contract pickling services. In India you might want to contact one of Avesta's representatives: Corus Liaison Services (India) Ltd 412 Raheja Chambers 213 Backbacy Reclamation MUMBAI 400 021 Tel: +91 22 282 31 26 Fax: +91 22 287 51 48 E-mail: kailash@corusindia.com Contact: Kailash M Palange

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