Use of 316 stainless steel in a marine envirorment
Use of 316 stainless steel in a marine envirorment
(OP)
I am designing a new system that will be mounted on the deck of barges. They will be mounted about five feet from the deck and exposed to the salt water air and an occasional splash from a wave. The old system used 304 that was time saved welded and not passivated. After three months these enclosures rust very badly and the customer was not happy. In the new system I am using 316L stainless steel that is time saved welded and passivated. I think this will help or eliminate the rusting problem, others here think the time saving operation is to blame and 304 smooth will do better than 316 time saved. We time save the enclosures to blend welded corners with the enclosure grain.
Any ideas on what would be the best method? Titanium or high nickel metals cost to much for this application. Is there a coating that would help prevent rusting?
Any ideas on what would be the best method? Titanium or high nickel metals cost to much for this application. Is there a coating that would help prevent rusting?





RE: Use of 316 stainless steel in a marine envirorment
RE: Use of 316 stainless steel in a marine envirorment
http://www.assda.asn.au/
has a download you may find helpful: 'Coastal Corrosion.'
Its recommendations to avoiding SS corrosion from salt include
1) Smoothness of finish (obviously, the smoother the better; an Ra of < 0.5 and/or electropolishing are recommendations),
2) Alloy. 304 is inadequate and 316 is OK "unless the job is aesthetically critical and frequent maintenance is unlikely."
"Where there are high aesthetic expectations a number of more corrosion resistant stainless steel grades can be considered (the first step up from 316 is 2205 and then the super duplex grades, high molybdenum austenitics and high molybdenum ferritics may also be useful). Smooth surface finish and maintenance are still important with
these grades."
3) Pickling and/or passivation after polishing, and
4) Regular washing.
RE: Use of 316 stainless steel in a marine envirorment
We will have our service people install these samples on the deck of the barge and see what happens. From prior experence it should take about three to four weeks to get rust to start showing.
RE: Use of 316 stainless steel in a marine envirorment
Flores
RE: Use of 316 stainless steel in a marine envirorment
The chapter 'Surface Finishing of Stainless Steels" in ASM Handbook, vol. 5 (1994) states the following:
"Lubricants may be in the form of grease sticks, waxes or cutting oils. Cutting oils generally are more effective when they are diluted as much as 4 to 1 with kerosene."
First, I hope that is useful information.
Second, my experience is mostly in the chemical treatments (pickling, electropolishing and passivation). What do you users with polishing experience recommend?
RE: Use of 316 stainless steel in a marine envirorment
Grinding stainless without acid washing ( call it passivating or pickling or anything you want) afterwards is guaranteed to result in poor corrosion performance.
RE: Use of 316 stainless steel in a marine envirorment
RE: Use of 316 stainless steel in a marine envirorment
While there are higher alloys that are more corrosion resistant than 316L, none of them will prevent the iron contamination from rusting. The reason being it is not the stainless or alloy that is actually rusting, but the small particles of iron on the surface.
RE: Use of 316 stainless steel in a marine envirorment
http://www.cromweld.com
It's used in a lot of "wet processing" type environments.
"The attempt and not the deed confounds us."
RE: Use of 316 stainless steel in a marine envirorment
RE: Use of 316 stainless steel in a marine envirorment
Sudipta
RE: Use of 316 stainless steel in a marine envirorment
Two such products are Derustit SS-3 from Bradford Derustit. www.derustit.com.
Another is Avesta Pickling Paste available from AvestaPolarit Welding Products 800-441-7343.
RE: Use of 316 stainless steel in a marine envirorment
As has been written in previous posts, Type 304 and Type 304L are subject to pitting in a marine environment. Type 316L can be used satisfactorially in a marine environment up to approximately 100 deg F. When the exposure to sea water spray routinely exceeds 100 deg F, the tendency for pitting increases significantly. More specifically, I have examined multiple failures of Type 316L tubing due to pitting corrosion in which the operating temperature exceeded 100-110 deg F. Type 317L instrument tubing should be considered in offshore applications in the Gulf of Mexico, South China Sea, etc. where the ambient temperature may exceed 100 deg F for extended periods.
Contamination of stainless steel with iron particles assures that pitting corrosion will occur. ASTM A 380 "Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems" provides methods to detect iron contamination using the ferroxyl test as well as methods to remove iron contamination. Cleaning with a solution of citric acid may be sufficient to remove embedded iron, and is much safer to use than some of the other solutions mentioned for passivation.
RE: Use of 316 stainless steel in a marine envirorment
I would like to know more about the ferroxyl test. Is there a kit available to perform this test? Is there a web site or book that explains how to do this test?
RE: Use of 316 stainless steel in a marine envirorment
See ASTM A380, Section 7.2.5.3 or
Method 102 of MIL-STD-753: Corrosion-Resistant Steel Parts:
Sampling, Inspection and Testing for Surface Passivation
(still available at http://assist2.daps.dla.mil/quicksearch/
get it before you have to buy SAE-AMS-STD-753)
"Copper Sulfate Test __ This method is recommended for the detection of metallic iron or iron oxide on the surface of austenitic 200 and 300 Series, the precipitation hardening alloys, and the ferritic 400 Series stainless steels containing 16% chromium or more. It is not recommended for the martensitic and lower chromium ferritic stainless steels of the 400 Series since the test will show a positive reaction on these materials.... Test solution:
Distilled water 250 cm3
Sulfuric acid 1 cm3
Copper sulfate 4 grams
Swab the surface to be inspected with test solution, applying additional solutions if needed to keep the surface wet for a period of 6 min. The specimen shall be rinsed and dried in a manner not to remove any deposited copper. Copper deposit will indicate the presence of free iron.
NOTE --If the copper sulfate test solution is more than 2 weeks old it shall not be used.
..."
Hint: Put the test solution in an eye dropper bottle.
RE: Use of 316 stainless steel in a marine envirorment
IF THE ORIGINAL 304 ASSEMBLY WAS WELDED AND IT WAS NOT THE 304L GRADE - THEN THE HAZ ON THE WELDED AREAS WOULD SUFFER FROM CARBIDE PRECIPITATION (THE CHROMIMUM WOULD REACT WITH THE CARBON AND THEREFORE DEPLETE THE CHROMIMUM). THIS WOULD OF COURSE RESULT IN LITTLE TO NO CORROSION PROTECTION AT THESE AREAS.
THIS CAN BE A PROBLEM IN THE AUSTENITE GRADES IF THEY ARE WELDED.
JUST A THOUGHT.
JACKBOOT
RE: Use of 316 stainless steel in a marine envirorment
You have had loads of excellent advice - even learned Shakespearian quotes - yet you may want to seek completely free expert guidance on both technical and cost aspects of your specific application by posting your question at www.nidi.org. That is the website of the Nickel Development Institute.
Good Luck