Take Time To Prep
More than one weld has been ruined by sorry prep work. Yes, I have done it myself, and any self-respecting welder will admit to having made a few rush welds that didn’t have the kind of prep work it needed with epic “fail” results. No, it may not be in a serious situation…or it may just be a small tack weld, but sooner or later we all allow impatience to get the best of us.
On the other hand, there are some welders that rarely clean or prep any weld, and seem to skate by. But when it comes down to it, almost all welds need prep work, whether to remove mill oil or scale, or to remove rust or some other form of contamination. These contaminants can cause weld brittleness and porosity, resulting in total failure of the weld. Even though the metal looks clean, it is not. With aluminum, shiny metal doesn’t mean clean metal. It should always be brushed with a dedicated stainless steel brush, and wiped down with aluminum cleaner or acetone. Even if the coating is mirror like, there is a serious oxidation layer present.
If it’s steel, mill scale and mill oil is almost always present. Grinding the surface with a stone disk(not a flap disk) is the best way to do it. Stainless perhaps because of its nature needs less prep work than other materials, but it should be cleaned well either by washing it or by a solvent like acetone. A word of extreme warning here: NEVER use brake cleaner or any chlorinated solvent to clean any metal to be welded. You will most likely die. Yep, that’s right!