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Will stainless steel 304 rust+++
Q. We purchased door pull handles from Canada. They were made from stainless steel 304 hair line finish and in polished finish. After installation on external doors, the hairline finish (US32D) showed rust marks. We tried cleaning but they always come back.
Is this normal for SST 304 US32D in high humid and hot areas?
Is there a permanent solution or we have to keep cleaning them. Are there any technical publication they states that this is normal for stainless steel 304.
doors and hardware - Dubai, United Arab Emirates
A. 304 WILL rust. 304 will rust faster in hot humid climates. 304 will rust very fast in hot humid climates as door handles frequently grasped with acid sweaty perspiration.
Clean the door handles frequently with rubber protective gloves and a rag dipped in 30% Nitric Acid.
Clean the door handles less frequently if you take them off the doors and Passivate in 50% Nitric Acid. The Nitric Acid oxidizes the exposed nickel into a controlled oxide and at the same time it removes the iron from the surface.
Robert H Probert Technical Services
Garner, North Carolina
A. By looking at the picture it is obvious that you have some pit corrosion on the surface. This is very difficult to remove! The nitric acid will not normally remove it. Some of the 304 stainless steel on the market today is not very good, but all 304SS is subject to corrosion in chloride atmospheres. Good lots of 304 should withstand the conditions you mention.
There are other formulations on the market that can help, but we have seen many situations like this recently that are constant maintenance headaches.
Stellar Solutions, Inc.
A. For true corrosion resistance in humid, saline areas like UAE, I believe you should COAT stainless steel with a clear thermoplastic - this retains the appearance of the finish and some manufacturers boast a 25 year warranty. Some sintercoat LLDPE thermoplastics have been in use for 21 years now, and have been very successful in South Asia, which has similar high UV, humid and saline conditions.
[LLDPE based polymers have greater adhesion to the substrate - the bond is chemical. Also, some LLDPE Sintercoat coatings are acid resistant, non-toxic, food & water contact safe and fire rated in a similar manner to pipe insulation- much safer in the event of a fire, where most of the damage is caused by smoke and fumes.
I was employed by a construction company, and I have witnessed doors constructed from SS316 corrode so badly over a seven year period they had to be replaced! [adjacent Victoria Harbour, HK]. At that time, we selected a plastic coating solution and our client was very happy with the result [so far!]
I believe the HK company with this coating recently re-opened offices in Kuwait for the application of this coating and may be able to help [I found them originally through the internet, they previously coated pipes, fences, steelwork etc etc in the Middle East [Kuwait; Dubai] many years ago -the applicator is based in Dubai also.
I wish you best of luck solving your problem.
- Hong Kong
It is a clear sign of Pitting corrosion.In a place like UAE, it is very common due to the saline air conditions.
It would have been better, had you specified the handles made of AISI 316L which could have given you much more longer life.The simple solution would be,take a 80 Grit Emery Strip & polish it with hand which will remove the Pits immediately. This can be done whenever you find the pitting.
- Nairobi, Kenya
June 6, 2013
A. We deal with this problem all the time. We are a global company who specialize in the correction and protection of stainless steel in harsh environment's, the worst being indoor pools. We find that regardless of grade (304/316) the tea staining or pitting will occur. This is mostly due to the brushed finish. Rolled or mirror finishes do not suffer from this.Tony Semple
- London United Kingdom