Newbie – Surface preparation for TIG welding

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Questions(a)Do groups of metals like ferrous, copper, alu need separate wire brushes/grinder wheels etc. like stainless does to avoid contaminating the surface ? (b)Would appreciate some help in identifying the finish /what tool is best used to prepare/remove the surface coating for welding/whether it can be welded (some items from my scrap box ) .Some indication on how much of surface coating needs to be removed / whether it is dangerous to health would also be appreciated (am trying to avoid galvanised surfaces ). ferrous_angle_bracket.jpg – yellowish shiny surfaceferrous_box_cover.jpg – painted box coverferrous_flat.jpg – I first used a wire brush on the grinder but it didn't removethe dark coating, then I used a grinding wheel on this piece and left the corner untouched – I think it is pre-base coated/not sure.Ferrous_handle_bar.jpg – nickle platedFerrous_pc_casing.jpg – not sure what the finish isFerrous_pc_casing2.jpg – this is a part out of a cheaper pc case – I think it is galvanisedFerrous_pc_power_supply.jpg – not sureFerrous_stapler.jpg – one side is green painted, the other I think is nickle plated or ?Ferrous_tape_player.jpg – looks like nickle but I'm not an expertAlu.jpg.- 1 piece of painted alu window profile and 4 pieces of alu profiles – forgotTo ask about anodised alu. Attached Images
Reply:more photos Attached ImagesLast edited by vjeko; 09-14-2010 at 03:22 PM.
Reply:Answer to a: Yes                b:  What the heck are you tig welding PC power supplies and tape decks for?????                    Some sort of robotic stapler??  Grind it down to bare metal and have at it
Reply:OK thanks !No robotic stapler yet  but art pieces/mods to electronic cases,  yes - was concerned that certain surface treatments needed "special attention" and/or care for health reasons.This and some of my future questions/threads may seem "stupid" or"what the heck is he asking that for" like, but my background is not inmetal working and have no welding school in the near, so would appreciatean honest answer.Could someone at least give an indication of what the respectivesurface treatments could be on the shiny/nickle coated like surfaceson my photos ?
Reply:Most of the parts you have likely have some sort of electroplate on them.  No way for us to know what it is really.  The Bicycle hanlebars are likely chrome plate.    The good thing is you really don't need to know.  Put on a dust mask and safety glasses and sand/brush the parts to bright metal in the weld areas and you'll be good to go.
Reply:Just so I'm not doing unecessary work /  overdoing the preparation,a few more questions:(a)preparation of steel surface - example is the third photo from top - metal hasa sort of "blue patina". If I use a very hard steel brush on an angle grinder, onlyrust is removed (any brown/black spots), the patina stays. So, does the "blue patina" need to be removed ONLY where I will be welding(in case paint will not be applied) ?If painting will be done, do I remove  all of the "blue patina" ? (b)For aluminium, from other posts, it seems a SS brush is good enough(no need for sanding/ use of power tools) - right ?(c)What about SS eg something that's been sitting inside and somethingwhich has been outside for a while ?
Reply:The "patina" on steel is called mill scale.  This is found commonly, and pretty thickly, on hot rolled steel.  Cold rolled steel has less of it.  If you want to TIG with really easily controllable puddle, and a really pretty looking result of well defined weld ripple pattern, the mill scale needs to be removed.  Sandpaper is a good way to do it, easily accomplished with an angle grinder or die grinder having a sandpaper disc or "flap wheel" (overlaid strips of sandpaper in a disc shape.)  You could also machine it off, file it off, etc.For aluminum, a stainless brush right before welding is useful for "abraiding" the invisible oxide film right before welding.  All other contaminantion, if present, will need to be removed additionally before hand.  Its a judgement call depending on how dirty the piece is to start with...  Solvents are sometimes helpful if there are any oils and grease.  If a clean solvent rag come up looking dirty, repeat the application until it comes up clean.  Dedicate your stainless brush to aluminum cleaning work only.  (no steels.)For stainless, if the surface is smooth, it may only need a washing, drying, and solvent degreasing if it was sitting outside.  But a quick going over with a stainless brush or sandpaper product to remove oxides near the weld area wouldn't hurt.Why not try preparing the surface for welding differently for one piece, and see how it affects the weld?  That way you can learn based on a controlled experiment, without just taking someone's word for it.
Reply:From what I have read and learned, it probably doesn't matter what metal you are working with concerning protection for your lungs.  I wear a respirator all the time, buffing, sanding, pre-weld prep, it doesn't matter.  If I am disturbing the surface of metal, I am wearing a respirator.  Search for "p100 3m".  That is the respirator I use and that I have read to be recommended by many.I would just plan to keep that thing on all the time while working with metals.Miller 330 a/bp water cooledI believe in gun control, I hold my gun with two hands.  If you want to know why, click here.Buy American or bye America.
Reply:I think that you will find a grinder invaluable.  A cheap grinder with a wire cup or abrasive griding disk will quickly remove the offending material.  In addition, you can use it to prep the edge of your materials with a bevel.Hell, get 3-4 of these and put different wheels/cups on them:http://www.harborfreight.com/4-1-2-h...der-95578.htmlAfter initial oxide/scale removal, a wire brush and a quick wipe with acetone constitutes decent surface prep for TIG welding.If you work with aluminum, keep a dedicated stainless brush and non aluminum oxide grinding supplies on hand.
Reply:OK, thanks for all the feedback ! - think I've sat through my class onsurface preparation now - onto practice and lesson 1 - "doing runs without filler"(back soon with more questions )
Reply:Vjeko.It is a good practice to ALWAYS use filler. If you have any desire to preform structurally sound welds you will need filler. Simply melting the parent metals to one another is not a sufficiently sound weld and in most cases will be very prone to cracking due to the shrinkage that takes place while cooling. Very characteristic of tig welding. This is exactly the reason why you "tail out" while doing roots on pipe. Start practicing with filler right off the bat.