Stainless Steel Sheets and Offshore Environments

this is anotrher good reference:

Atmospheric Corrosion Resistance (318) A discussion of the corrosion resistance of the AISI standard austenitic stainless steels in rural, industrial, and marine atmospheres, with tabular data. Included are brief discussions of architectural, structural, transportation and hardware applications and the use of stainless steel insect screens

http://www.nickelinstitute.org/index.cfm/ci_id/15786/la_id/1/ci_doc_id/3214/search_keyword/1983/method/3.html

S

corrosion protection

thanks mo much sceptic and strider4. Your information really helps but do we need to paint for the finishing touch or just let it be bare SS316?

Depending on design and the importance of appearance vs function, it shouldn't be necessary to paint either SS or Al.

painting ss is quite tricky and it is probably best just to leave it bare. easier for cleaning and you won't risk the paint peeling off.

12% Chrome is also a good spec for this application. Unpáinted or painted.

the aluminium can be expose without paint cover? Oh, but the aluminum maybe to light for me to fabricate a cabinet or enclosure to put all the membranes and instruments+piping which nearly 2 tonnes in weight. It will give me a hard time when we are lifting up the unit. So, maybe we just use the SS316 instead of aluminium.

"No one mentioned fiber(glass) reinforced plastic. Isn't this a fairly common solution for controls cabinets in a salt water environment?"

If the cabinet is exposed to the sun in areas like the tropics, it has a short life.

At Mt Isa (dry tropics, about 17.5 S latitude, semi desert environment), fiberglass grid flooring exposed to the sun deteriorated to be unsafe after only 18 months. The area which was shaded by a nearby building was still OK. We had been assured that testing in temperate climate latitudes had shown it to be OK in this environment.

I have been suspicious of all plastics in exposed locations ever since, especially in high solar exposure areas like the tropics.

For boats, fiberglass is given a sacrificial gel coat. If you look at these after some years in the tropical sun, you will find the gel coat is chalky and can be scratched off with your fingernail. In extreme cases, sections of the boat need to be cut out and replaced.

If the cabinets will be out of the sun, then fiberglass should be OK.

I think unpainted 316SS would be the safest bet. 5083 Al could be made strong enough for substantial loads and would be my next choice. 304SS may be prone to pitting corrosion which is why I would prefer 316.

Thanks for the insight!

I have seen many problems with aluminium in marine environments, whether it be 5083,5086, 5754 and some of the 6000 series Al/Mg based alloys...................I will try and get some photographs of some of the aforesaid items.

Just curious............would a non-metallic finish be an issue, e.g. fibre glass.

Hi Azreen.

Our company is delivering (engineering / manufacturing / testing) equipment to the offshore oil & gas industry. We also deliver cabinets for electric and hydraulic equipment as part of the different projects, and we always use material AISI 316 L in the cabinets. We have not encountered any problems with our cabinets due to corrosion. Be aware of problems if you are welding the cabinet in an enviroment where there also are produced items in mild steels. (If you are using grinding tools for mild steels on your ss, or even storing your ss materials in a workshop for mild steel, your ss could be contaminated).

Hope this info can be of some value to you.

I would suggest type 316 SS or any of the 5000 series aluminum alloys. In the shipbuilding industry, aluminum alloys because of their resistance to corrosion and their light weight are used mostly in areas exposed to saltwater. It is painted to resist oxidation and to provide a final finish. No material when used in a marine environment will last forever. Maintenance is still required.

Your last two sentences ring true with me. A retired Navy submarine skipper I work with half-jokingly states, "Salt water corrodes plastic." Just his way of saying nothing seems to be impervious to the salt water environment. We build things out of expensive metals like titanium, K-monel, Inconel, etc. and we have a noted expert on corrosion on the staff to help prevent us from making mistakes in the field.

Grade 310 and 310 S are higher Chrome and Higher Nickel grades with excellent corrosion resistance. Most applications of this grade are for heat resistance, but Carpenter reports no evidence of stress corrosion in marine exposures at levels up to 90% of yield strength. Probably over kill, but the expense of failure is substantial...I know these are available in sheet.

Proper passivation is the key to success with any stainless grade after fabrication; proper isolation frrom other metals is the key to success in installation. Attention to these details will minimize possibility of corrosion.

milo

Hi Milo,

How goes the battle?

Grade 310 and 310 S are higher Chrome and Higher Nickel grades with excellent corrosion resistance.

One could always go the whole hog and use one of the superalloys.

Just a point of interest on this subject.............in marine applications, such as internal valve components, valve spindles, centrifugal pump rotating assemblies, propeller shafting, etc...............super alloys are the preferred materials e.g. Monel, Iconel, Invar, Nimonic etc...............however SS can be used but, not preferred.

Our comments have changed the draft regulations but everyday reveals yet another unanticipated application that would be forbidden. I guess its time to post on this subject.

Thanks for the hiddee ho.

milo

thanks guys for all your comments and ideas. This forum really helps us to share all knowledge that we have so that we can improve ourselves and future technology.

Normally type SS 316L is used for offshore equipment that are used as cabinets, but if you have used CS, there are some kinds of marine paint that is proper for those environment, you may find more info from marine paint manufacturer as Internation Paint or Hempel.