Marine Corrosion of Stainless Steel

A. Mike:

This can be a difficult problem in the salt spray. If the railings are 316 stainless steel, you should be able to passivate them to remove any residual iron on the surface and then it may not need a coating. If it is 304 or other 300 series, it may not stand up to the salt spray for very long.

Passivation in the field can be done with citric acid based pastes.

If you want to coat it to make sure that it is not ever going to rust you need to talk to a good coatings company. Good silicone based formulations can work, and they are resistant to the UV from the sun. The problem with coatings of ANY kind is that they can eventually start to peel or discolor. Then you have a major problem of rework or replacement.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2001

A. Dear Mike,

Why don't you use titanium for your articles. Titanium has unique corrosion resistance in sea water.We use titanium greatly (Russia).

Andrey Igolin
- St.Petersburg, Russia
2001

A. Ahhh yes, I would love titanium railings. Just bring money! Seriously, I have "tested" a number of products to coat SS railings on boats. Coatings that are painted on or sprayed on often look diseased within a year! Removing them is a LOT of trouble. If your railings are at least marine grade, then there are a great many products out there that will clean and then put a protective coating on the metal. This is a lot of work if your railings are heavily corroded already. For a review of products, you might look at "Practical Sailor" magazine [at www.practical-sailor.com]. It is the Consumer Reports of the sailing world. They perform field tests of products.

My own preference has been a product that contains Teflon in it as part of the coating, rather than just a wax. I put two coats of this stuff on in the spring, buff it up and it endures heavy salt spray with very little spotting for about three months or so. This is on the bow railing. On the stern (where the spray is less), 6-9 months will pass before the rail needs to be cleaned and coated again. I suppose a coating on your railing may last a year, unless you receive direct salt water spray on it. In any case... having nice shiny metal in a marine environment is always a lot of work!

If someone has the answer, I sure would like to know, too! Now if you were replacing the railings... you could consider bronze or chrome-plated brass. Each of those has its drawbacks, though, and thus, I prefer the stainless as a material.

Ronna Erickson
- Amherst, Massachusetts
2001


2001

A. Mike,

I hate to be negative (in fact I enjoy it!) but why metal AT ALL when in most cases {Ti and exotic Ni alloys excluded) you only have two options.

Posts etc from stainless, maybe, but rails from glass?

Posts etc from stainless, maybe, but rails from PVC.

You can get PVC piping in two really exotic colors. White and grey. Over a long period of time (U.V. attack not salt) the grey will blanche slightly. Low cost. Zilch maintenance.

I'm not sure about Monel ... after all this is a seagoing NiCu alloy and ideal for shafts ... but is it available in piping? I dunno.

Am surprised no one has suggested rhodium plating your stainless ... but as you must have enough $$$ in the first place to chose stainless, then, as the man says, go to Titanium....

The Germans have a lovely proverb,'wer die Wahl, hat die Qual' which in essence means 'decisions are painful'. So keep the Lamborgini (sorry, Jaguar) and use PVC!

Cheers!

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

A. 316 Stainless Marine grade stainless steel can be rendered corrosion proof by application of [a nylonic polymer] initially invented for Apollo moon shot lander, etc. We have used this product to completely protect and renovate corroded stainless steel in olympic pools /exterior situations etc including public sculptures with long lasting results in New Zealand and Australia.

John Fielding
- New Zealand
2002


2002

A. Hi, John. I don't understand using a very expensive metal like 316SST if you are going to depend on a coating to provide the corrosion resistance. What am I misunderstanding about this approach? Thanks.

Readers: This site is for technical discussion of approaches (such as nylonic polymer) not for suggestions of specific proprietary products -- no brand names please.

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

A. I have used [nylonic coatings] sorting out stainless around some of the local beach resorts, where 304 and 316 railings have rusted by either salt or other untoward corrosive things ... Dust from the desert here is largely iron oxide so rust can be pretty bad. [Nylonic coatings] were used on US Satellites that they recovered from the sea in water landings - when it was the only method... [nylonic coatings] have been around for years but was hidden away under a Government patent.

Jeff Melville
- Sydney Australia
2003

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A. G'day all!

I would just like to add my 2 cents worth to this debate.

It is my understanding that adhesives which are generally used to make a coating stick to a surface, generally start to break down after 5-7 years; this being true, if you were to use a coating for the stainless that contained an adhesive, at some stage it would require recoating. So in my thinking one then has to look at the ease of which the stainless can be recoated e.g., ease of coating removal, etc.

As it is my understanding that no advertising of products should be done in this forum , I will refrain ha ha ... however, there is a coating that will achieve the results on stainless that some earlier posts have eluded to (and as you probably guessed it doesn't contain any adhesives) it will last as long as the surface of the substrate to which it is applied. Anyway as I said, just chucking my hat into the ring ha ha have a great day Rod!

Rod George
- Australia

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Ed. note: Thanks, Rod. Yes, we ask people to not offer testimonials. This site is for technical education, and little is learned from claims that Secret Formula X is better than Secret Formula Y. Plus, it encourages a race to the bottom, with sellers even posing as satisfied customers :-(
It also encourages spam, and we can't ask the advertisers who make this site possible to pay for ads by their competitors, or police checks to determine if "satisfied customers" are real. No brand names please.