Where the
world gathers for metal finishing
Q&As since 1989


-----

Stainless steel rusting

 

My company is a maker of stainless steel wine tanks. Our wraps are of 304SS. Our clean up of welds on the inside consist of using a ss wire wheel. We do get some rusting around the welds, which we neutralize with acid. I am looking for a better way to clean the welds without the acid.

Thanks,

Kier Koponyas
- Penticton, B.C. Canada

Welding certainly does not help the corrosion resistance of the SS. The major problem is the da@n wire brush. Most SS brushes are of the 400SS series which have poor to bad corrosion resistance. What it does is put millions of tiny pieces in the surface, which are dissimilar metals and rusting is virtually guaranteed as soon as there is moisture present. Try using flapper wheels (sandpaper) and finish with scotch bright wheels.

James Watts
- Navarre, Florida
 

---

Kier: I agree that from my experience the problem is many times the wire brush. Regardless, the weld will always be the weak link if it is not passivated. We recommend polishing with a Scotchbrite pad or belt, then clean and passivate the weld with one of our safe citric acid formulations. Let us know if you need help. Lee

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

 

---

 

Kier,

What Lee and Co said is l00% correct. You should use an acid of some sorts (Citric?) to help in passivating your welds.

However, for future tanks or for any rewelding, consider another approach.

Why not use a MUCH higher grade stainless weld rod ... or, presuming good tensile adhesion, just good ole plain Nickel.

However, on retrospect, you'd probably get some ferrous particles appearing on each side of the weld which would have to be treated.

Lastly, tongue in cheek, you could promote your wines as Fe203 enhanced ! ... in which case you'd do nothing to the welds.

Your problem seems to be terribly, terribly common. I personally believe that it has to do with the temperature at which the welding is done because obviously all the main s.s. ingredients have different melting points, don't they? And if you exceed these temperatures, ask yourself, what happens !

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

---

Use pickling paste ie.acid paste or jell to remove weld stain then flapper wheel i.e., scotch brite with sanding pad combination. You may wish to use polish mop after depending on required finish. When welding main body of tank use double welding technique to keep heat at correct temperature.

Double welding. When welder on inside of tank fuses simultaneously with wire feeding welder on the outside.

Steve Blick
Quality Sheetmetal - Invercargill, New Zealand
 

I don't really know the answer kier, but I can tell you how to play an instrument...just thought I would say hi...your bro.

Todd Koponyas
- Fort St. John, BC, Canada