Stainless Steel Railing Rust & Corrosion Problems

A. Hi Thomas. Yes, passivation needs to be done, but it can be done in situ. You can do it yourself or have it done with citric acid; or you can retain a professional to do it with the more dangerous nitric acid. The sooner the better because once pitting starts it's more difficult. Good luck.

A. Thomas,

What was the abrasive in the 180 grit that you finished the railing with? I have a gut feel that it was not aluminum oxide but rather a flint or iron based abrasive. It could be aluminum oxide or other abrasive embedded in the SS providing sites for corrosion to spread. I welcome feedback here. You may have to on site remove the visible rust, and doubly good on welds. Use a "Scotch bright" abrasive wheel. Clean well and use the gel citric passivate from Stellar Solutions [a finishing.com supporting advertiser].

A. There are several possible causes for this corrosion problem.

1) If corrosion becomes visible as soon as a few days or weeks after installation, the most likely cause is carbon steel or iron contamination of the surface. If it is surface contamination rather than deeply embedded particles, a surface chemical treatment can dissolve the carbon steel without damaging the stainless steel. Citric acid passivation products can be used but they are generally less effective than other options. There are Nitric acid gels which can be painted on in the field and then rinsed away. They can be tough on surrounding plants because they can be the equivalent of over fertilizing. Oxalic acid [on eBay or Amazon] can be effective if you want to try an intermediate step before stepping up to a nitric acid.

Both Barkeepers Friend [on eBay or Amazon] and Zud [adv: Zud on eBay or Amazon] contain oxalic acid and fine abrasive that will not scratch the finish. Make it into a paste, apply to the surface and let it sit on the surface for 10 - 15 minutes (giving the acid time to work) before rubbing. Thoroughly rinse off the paste. These contain some chlorides and could end up causing corrosion if not completely removed. I would suggest cleaning a small area with the product and then doing what is sometimes called the "wet diaper test". Take a diaper and thoroughly saturate it with water. Wrap it around the "clean" area. Tape to hold it in place and prevent moisture loss. Remove after 48 hours and see if the corrosion has returned. You can use a cotton cloth and wrap plastic around it instead of using a diaper. This accelerates the moisture exposure that would occur naturally over a couple week period. If there is no corrosion after 48 hours, you can assume the cleaning product will be effective. If it is not, you will have to use a more aggressive product. In the worst case, pickling or refinishing may be necessary.

2) The corrosion could also be caused by exposure to Muriatic acid (hydrochloric acid) if someone happened to clean stone, concrete, or masonry nearby. Alternatively, someone might have used a "stainless steel cleaner" on the railing that contains hydrochloric acid. There are some very questionable "stainless steel cleaners" on the market. This acid can is very corrosive to stainless steel. If this occurred, neutralize the acid with Chlor-rid [on eBay or Amazon]and determine if the corrosion is bad enough to require refinishing.

3) The other common possible explanation will be dependent on the time of year when this was installed. If it was exposed to deicing salt shortly after installation, the following could be the cause. Type 304 is not a good choice for exterior applications in areas that use deicing salt or are exposed to coastal salt. It will corrode. Tube/pipe railings are often made from higher sulfur stainless and the sulfur inclusions can be sites for corrosion to start. The relatively rough finish could add to the problem, particularly if you used alumina abrasives. Always always use silicon carbide abrasives and replace them when they start to wear. Silicon carbide cuts the surface cleanly on a microscopic level which is important for good corrosion resistance. Alumina actually smears the surface on a microscopic level and those micro crevices greatly increase susceptibility to corrosion. For Type 304 to work in exterior applications exposed to salt (chlorides), you must use a very smooth finish (minimum of 240 grit but 280 to 320 would be better). Use silicon carbide abrasives, and plan to clean it every spring to get rid of salt and light staining before higher temperatures and humidity accelerate the corrosion.

* FREE *

Type 316 with a smooth finish is usually the best choice if you want to avoid maintenance. Stainless steel finishes and architecture are my area of expertise. I have written several brochures on selecting the right stainless steel for applications and preventing atmospheric corrosion of stainless steel for non-metallurgists. They are available free of charge from the Nickel Institute, Reference book series 11 024 "Stainless Steels in Architecture Building & Construction: Guidelines for Corrosion Prevention" ⇨ ⇨
and International Molybdenum Association, "Which Stainless Steel Should Be Specified for Exterior Applications?"
I think the first of these in particular would be a big help to you.

I hope this helps.

A. I am sorry to hear that you are having problems. Type 316 is the right stainless steel to use and it should have provided corrosion free performance. The rapid rate of corrosion is a good indication that the surface was contaminated with steel or iron particles. This could happen if someone "cleaned" with steel wool, cleaning pads that had been used on steel, or if the fabricator did not adequately protect the stainless steel during storage or fabrication in the shop. Your commentary suggests that they should take the time to learn more about stainless steel before working with it again or giving advice. The result is steel particles on the surface that are corroding like bare carbon steel that is exposed to a coastal environment. Staining can take as little as a few hours or as long as a few weeks to appear when there is contamination dependent on temperature and humidity levels.

There is no need to use wax on stainless steel that is clean (no embedded iron) and it could have an adverse impact on corrosion protection. After you resolve this problem, stop using it. See if the container suggests how to remove it from surfaces and clean it off the railing before trying the following.

If the contamination is superficial rather than deeply embedded, it may be possible to remove it using either Zud [adv: Zud on eBay or Amazon] or Barkeepers Friend [on eBay or Amazon] (I am suggesting these because they are household cleaning products that are usually readily available.) Make the powder into a thick paste and spread it onto the surface. (Either premix the paste or sprinkle the products on a clean sponge or soft cloth that is moist enough to create a paste when rubbed on the surface. It is best to do this during a cooler part of the day or when the railings are not in direct sun so that the paste stays damp while you are using it. These products contain oxalic acid which will dissolve iron/carbon steel and remove it but will not harm the stainless steel. The fine abrasive can also help remove the carbon steel. Leave the paste in place for 10 to 15 minutes and them start rubbing along the grain line to remove any remaining staining. Rinse off the cleaner thoroughly or it will leave a white film. This is messy but it often solves the problem after one or two applications. You might want to try it in one area to see if it makes a difference before cleaning all of the railings. Never use Comet, Ajax, Softscrub, or similar common household cleaners. They can scratch the finish and some contain chloride compounds that can cause corrosion if they are not thoroughly washed off surfaces.

If this does not work, the carbon steel could be more deeply embedded and it may be necessary to remove the top layer of stainless steel (refinish). Stronger acids could also be tried but I would worry about surrounding materials and the person applying them. If you still have corrosion problems after cleaning with the products above, the contractor should refinish. They need to use new, silicon carbide sandpaper (not aluminum oxide sandpaper!) which should be replaced as soon as it starts to wear - starting with coarse and then using gradually finer papers to get the desired final finish (preferable as smooth as possible for maximum corrosion resistance).

I hope this works.

A. In my years of experience of finishing stainless steel handrails/welds, etc..I would suggest refinishing the handrails in situ to a finer grade finish, i.e., 240, 320 or even "bright" or "mirror",thus removing any deeper "scratches" that permit oxides etc to "cling" to the finished surface.

Adv.
Scratch-B-Gone for Stainless steel quickly dissolves the rust and restores the grain pattern on architectural rail systems and leaves behind a protective coating to repel future rusting. In an accelerated weather test, the chemical treatment withstood 72 hrs of 10% NaCl fog and showed no rust return. Remember Scratch-B-Gone(.com) for rust on your Stainless! All repairs done on-site and non-invasive.

A. I will advise you to make Mirror polish on these railing because mirror polish helps you from corrosion for 2 or 3 years. And I suggest you that if outside railing then always use 304 grade material it has corrosion resistance and 304L is better than 304.

Because 304 grade Carbon content: 0.08%
and 304L Grade tubes Carbon contain: 0.03%

Hope it will be helpful for you.

A. Hi Gazali,
I don't know much about railway equipment, but presumably you are not talking about rails which, I believe, must be made of specific steels for strength and wear-resistance needs, rather than of corrosion-resistant stainless steel. What sort of railway equipment please?
Luck & Regards,

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

A. Abhishek,
Would you say the red is a rust color? When you apply the #4 finish, do you use equipment that is used only on stainless, or is the equipment used for carbon steel also? How is PVC involved here?

A. Hi Abhishek,
Presumably the PVC is a protective film which is kept on until the stainless steel sheet is installed and put to use? The sheet may not have been passivated or it may not be up to withstanding the specific environment. Can you tell us more?
Luck & Regards,


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

Hi Aravindan. The robust way to address this problem is to start with 316L or 316Ti stainless steel, which is designed to prevent carbide precipitation and consequent corrosion in the weld areas. Some premium cookware manufacturers use that. What are your utensils and appliances made of?

Passivation, perhaps with pickling paste, should be done but may not solve the problem.

Regards,