I use GumOut 2+2 carb cleaner, it cuts the oil etc and dries quickly to make it safe when welding. I also use scotchbrite pads on an angle die grinder on the difficult stuff befor carb cleaner. There are horror stories using carb cleaner when welding, the fumes cause brain damage so be sure you use high quality cleaner that evaporates quick. A br*** tootbrush style wire brush is handy too, the stainless ones can contaminate the weld.
I use acetone and a stainless brush that I only use for aluminum . Go to a site called weld****ers.com they are also on u tube.
Old aluminum over the years will corrode and the worst part it's very porous and soaks oil deep into it. Regardless how well you clean aluminum heating it will draw more impurities.
True words here. In years past I had a boat propeller repair shop. Many aluminum props when welded to repair edge damage would have pits appear in the parent metal, just adjacent to the welded area. These were cast aluminum, with the Volvo inboard/outboard props by far the worst . Sheet, or plate aluminum not as bad with these pits.
Are you welding sheet material or cast stuff? Petejoe is right about the cast aluminum stuff - it's amazing how much **** floats out of it - If you're going to grind the welds down afterwards, "V" the weld area, use plenty of amps to float the **** to the surface, and clean it with acetone before welding. Sheet stuff I usually hit with a scotchbrite disc, clean with acetone. The selection of filler material will certainly affect the appearance and cleanliness of the puddle, try to match it with the base material - there's lots of information out there as to what filler to use with what base material.
I clean with lacquer thinner, if it's a casting I sometimes p*** a propane torch over the area prior to welding. That way you can bring any impurities to the surface, and wire brush for a final cleaning before welding.
Lincoln recommends: Base-metal preparation: To weld aluminum, operators must take care to clean the base material and remove any aluminum oxide and hydrocarbon contamination from oils or cutting solvents. Aluminum oxide on the surface of the material melts at 3,700 F while the base-material aluminum underneath will melt at 1,200 F. Therefore, leaving any oxide on the surface of the base material will inhibit penetration of the filler metal into the workpiece. To remove aluminum oxides, use a stainless-steel bristle wire brush or solvents and etching solutions. When using a stainless-steel brush, brush only in one direction. Take care to not brush too roughly: rough brushing can further imbed the oxides in the work piece. Also, use the brush only on aluminum work-don't clean aluminum with a brush that's been used on stainless or carbon steel. When using chemical etching solutions, make sure to remove them from the work before welding. To minimize the risk of hydrocarbons from oils or cutting solvents entering the weld, remove them with a degreaser. Check that the degreaser does not contain any hydrocarbons.
India Pale Ale is what you soak your head in to get rid of the jitters if you need it. IsoPropyl Alcohol is a good cleaner. Good Luck
There is a very good tutorial for welding cast aluminum on you tube by Jim Bollinger at DoRite Fabrication. He is an instructor for Lincoln Welding, and also runs a job shop… Making it easy to find the ***le is Welding a cast aluminum part….
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