Stainless Steel / rust from salt air

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I am new to welding, my daughter talked me into a few classes here at Ventura College.  I have a new Lincoln TIG 185, I am just a home hobbiest and not a "good" welder - but having a really good time welding stuff for our small ocean boat.  I have been sticking to aluminum as it's easy to cut, file and shape.  I have done a few projects with left over stainless steel we have from boat parts and such.  My problem is the project rust like crazy near my weld.......not so much the bead, but up higher.  Again, I'm not so great - and I know I spend too much time in one area getting my project WAY to hot. Does anybody know what the pro's do? I feel the stainless that I am using is of good quality - as they looked great till I got my hands on it. Maybe I am not "polishing" or buffing out the SS well enough?  very odd.Any idea's would be of great help, THANKS Donna
Reply:Is there any way you could post a few pics Donna???What grade of stainless is it??...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:The way I understand it, once the stainless is welded, you have to wire wheel the heck out of it to bring the stainless to its shine.  I think it brings out the nickel or chromium out of  the stainless.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:what grade stainless steel are you using ? 304 L has a higher carbon content then say 316 L . Are you using a stainless steel brush on your weld ? Are you using a file on your weld ? It could be many things other then just these . I be glad to help you just need more info .
Reply:One of the major important factors in welding stainless (besides heat input) is shielding gas.  Make sure that you have good shielding on your weld...that will help prevent the rust.
Reply:I weld SS on boats here in HB, Neweport bch. a lot. To get rid of the rusting issue, don't use a wire wheel. ESPECIALLY if you are going to polish the weld. 3M makes some abrasive pads, and there are scotchbrite pads that go on a wheel. Use these scotchbrite pads first, to knock off the dark areas, and to buff down any welds that are a bit lumpy. Then, the rubberized grey 3M wheel will put a mild polish on the weld. That will literally seal the area up as it smooths out the scratches. It is in the mini scratches you will get the worst rusting. If you are looking to polish the SS, then use some cutting compound/ black magic for the rough polish work. Then, top it off with white rouge on the buffer. Try to shield your welds from outside wind- the less wind, the better. Blocking the wind is more effective and cheaper than just turning up the gas pressure.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:A well made SS weld will not have a rust issue and does not need to be wire brushed or polished in any way to be made rust resistant.  A couple of things to think about.1.  As others alluded to, do not use any carbon steel wire brushes on SS, and do not use grinding wheels that have been previously used on carbon steel (or aluminum), since you may actually deposit carbon steel onto the SS which will then rust.  Only use clean SS wire brushes on SS.2.  SS is prone to carbide precipitation (ppt) which can reduce the corrosion resistance in the heat affected zone (HAZ) next to the weld.  (Search here for previous threads on this).  To minimize carbide ppt, minimize weld heat input and rapidy cool the weld to minimize the HAZ, use low carbon SS grades such as 304L or 316L, or use stabilized grades such as 321 or 347, and provide good inert shielding for the weld so that HAZ discoloration is light straw with minimal blue or darker shades.
Reply:I don't know what grade of SS it is - they were some left over "Perko" rod holdlers (for those of you who deal with boat stuff would probley know that name brand of accessories) that I welded to an existing Perko handle on my engine cover.  I do weld in my garage so I should have good gas coverage (no wind, and if it is windy I close my garage door.  I still haven't learned to post photo's - and to tell you the truth......this project's weld is pretty horrible...I would hate to post them (way too embarrassing), but the rod holders work very well in their new location (so I did do that right)  I guessing from everybody's replies the two things I didn't do right are: polish them well enough after the weld, and way to much heat while welding...which is something I know I must work on as far as welding practice, as sometimes I have a hard time starting a bead.I will go out and polish the crap out of them and see if that helps.I do need to get more educated on the different grades of SS and aluminum, as I have made lots of stuff for the boat and have made two steps for our truck camper out of aluminum.  Do you guys have a website that might spell out the different grades and what they are used for? Something that the average person could understand?Thanks so much for the replies.Donna
Reply:Another thing to try is to passivate the stainless with acid.  I'm working on trying that now so I can't say if it works long term or not.Somebody recommended nitric acid on another forum and so does the following article so that's what the first test will be.http://www.mmsonline.com/articles/100304.htmlOh and before I forget, I am in the middle of doing some boat stuff (will post project pics soon) and 316 seems to be the grade of choice.Favorite right now is a Miller Syncro 200.Tons of tools and I blame at least one of them when things don't go right.
Reply:Since you describe your problem as outside the weld bead area I think you have high carbon content stainless base metal. Even if you use low carbon electrode 308L or 316L you are still going to have the same problem. The proper way to solve your problem is to use low carbon base metal. Or, heat treat the welded structure after you have completed all welding. I do not know the exact procedure to dissolve the chromium carbide and restore the stainless quality of your original part. It depends a lot on the size and shape of your project. I don't heat treat because it is a pain and the parts I use are too big to fit in anything other than an industrial heat treat oven. I do know you need at least 1600 degrees f, maybe more. A good bet might be to find a neighbor with a pottery kiln.A cheap fix it to just treat the heat affected zone like mild steel and paint it after sandblasting it. Use a good grade epoxy paint or better yet powder coat it with clear.