Mig on rusty metal

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Im getting a mig for shop use and to fix things for my ranch. I was wondering how tempermental mig welding can be when it comes to welding on rusty material. I see a lot of people showing off their welds and it appears that are welding on steel that is almost fresh from the mill.For me that would be a perfect world but we all know thats not possible.I start of with a rusty plate and usually hit it with a brush wheel.  Will that be enough. I also weld through painted material sometimes. This is all 6010 STick welding..Will I have trouble with my MIG...What have you guys learned about it or done.
Reply:The cleaner you get the metal the better your weld with mig. You can get by with things welding with stick electrodes that just won't work with mig.
Reply:Flux core wire welding will go thru more rust and paint than Gas mig. Don't expect 6010 performance from any wire welder however. Wire brushing, even on a grinder will not give you high quality welds on very dirty steel. You will need to grind to semi clean steel at a minimum. Will it hold a piece of sheet metal to a rusty post yes. Will it do good structural welds on rusty and painted heavy steel with little to no prep, NO.
Reply:yeah thats what im worried about. All my stuff on the farm is rusty (naturally) so i brush wheel it off. the metal is still rust colored (not fresh looking)  Will this work.....
Reply:A brush wheel will only polish the rust. When you apply some sanding paper, the rust appears again. Grinding removes the rust.
Reply:Sorry there's no easy answer. What will you weld? How dirty and rusty is it? How strong is good enough? Can you stick metal together? Yes. Will it be strong enought to hold up? Maybe, can not say with out seeing it.Lots of heavy equipment repairs are done with flux core wire. Again prep is key. Does it need to be as clean as tig, NO. That said there are reasons that stick welds using 6010 are still being made and are often made on heavy equipment. Time is money, 6010 will make good quality welds on material with little to no prep that could not be made with FC without more prep time.Both stick and FC wire have a place on the farm. Neither will completely replace the other. But stick does stand out on dirty material, better than anything else.Last edited by DSW; 06-04-2008 at 01:19 PM.
Reply:Originally Posted by chadwickz71Will I have trouble with my MIG...What have you guys learned about it or done.
Reply:well I understand the point. I've been stick welding for 7yrs on all kind of stuff here where i live. I don't think i'll have a problem I'll just have to do a little prep work here and there.Any hey with the 350mp, if I ever run into a problem i'll just plug in my Stick leads and show it who's the boss! Right!!
Reply:Originally Posted by chadwickz71well I understand the point. I've been stick welding for 7yrs on all kind of stuff here where i live. I don't think i'll have a problem I'll just have to do a little prep work here and there.Any hey with the 350mp, if I ever run into a problem i'll just plug in my Stick leads and show it who's the boss! Right!!
Reply:Yep.  Dead things can't be the boss as we Dutch say.The old Accetylene torch will do the job also. The flame is full of CO which will reduce Fe2O3 to Fe and CO2.The same happens with a bit CO2 welding the arc turns some CO2 into CO which will do a bit of reducing.For the rest you'll have to depend on what's in the filler or electrode.
Reply:Look at the welds posted here.   There are lots of pictures of beautiful welds.  ALL of them are done on clean steel.  If you want a good quality good looking strong mig weld, clean off all rust, paint and mill scale.  Just do it.No amount of machine will make a good weldor out of a sloppy prep job.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Just a mention here .....   hard wire, with straight 100% C02 shielding gas, a reactive gas, not inert, will do better with rusty metal, painted metal, and galvanized metal, than almost any AWS classified flux-cored  wire.
Reply:ER70S6 wire with an Argon/Co2 combination will also work, the S6 wire has some extra deoxidizers added to it to help burn through mill scale, paint, rust etc. Higher Co2 concentrations will also help, if you don't want to run straight Co2, try a C-25, C-20, or C-15
Reply:Let me put my fire suit on a minute.... Okay I'm ready! Core wire with heavy deoxidizers and CO2 shield, burned hot with spray transfer, will produce excellent quality welds on rusty dirty painted used steel. My favorite wire for "dirty work" is Fabco RXR, but it's strictly for flat work.
Reply:Originally Posted by ss42768ER70S6 wire with an Argon/Co2 combination will also work, the S6 wire has some extra deoxidizers added to it to help burn through mill scale, paint, rust etc. Higher Co2 concentrations will also help, if you don't want to run straight Co2, try a C-25, C-20, or C-15
Reply:When you get right down to it prepping your metal by grinding to bright, shiny metal will give you a better weld with ANY process, not just mig. And that weld is easier to make with clean metal.
Reply:Thanks guys for the input,By the way Im not saying Im to lazy to prep but about 1/2 the stuff I do is in spots that are almost impossible to clean with a grinder much less anything else. And yeah there isn't rust just flacking off but it is discolored from new steel. Also there are instances when im fixing a spot that involved welding over or through a little paint, but I just can't hardly help it. Im just looking to see what I can do if anything to help me out.  I guess its a little bit of trial and error. Problem is I don't know very much at all about shielding gases and whats scary is the people at me LWS know even LESS!  Its sad buy very true.Thats why im talking to you guys, and I do really appreciate it!
Reply:I just read this on the Miller website.http://www.millerwelds.com/education...article62.htmlEverything I have heard so far said just to make sure the surface is clean, so I was planning on just doing that everytime.  But this might be some useful information if you HAVE to weld on a piece that you just can't get properly prepped on the farm.  I had just read this post before finding this information so I thought I would pass it along.Although more expensive than solid wire, flux cored wire could help you gain productivity. Flux cored wire typically has the ability to handle the welding of dirtier materials that may have higher levels of rust, mill scale, or oil. Although cleaning is always the proper method of preparing the steel, flux cored wires contain de-oxidizing elements that trap these contaminants in the weld pool and hold them in the slag coverage typically preventing the associated weld problems found when welding "dirtier" steels. Flux cored wire also increases penetration on the side walls and offers the advantage of better deposition rates (the amount of weld metal deposited in a given time period, measured in pounds per hour) when compared to solid wire. Although the operator is initially spending more on materials for flux cored wire, the savings are realized in the decreased production time.