A common question: For aluminum, how clean is CLEAN? And, what is 'Clean Enough???'

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It gets asked a lot. The answer is always the same; CLEAN, or CLEANER STILL Dude!! But in reality, as with all welding, most of it is not on new material exclusively. Much of it is not on a known grade or quality of material. Many times, there simply is not enough money to justify going berzerk with the cleaning process. And, what of this Aluminum Oxide we read about so much?? How bad is it, what does it do??So, I'll give you some hints as to what I have learned over the years.On clean, brand new billet, or plate aluminum: Especially stuff stamped with a grade, and you know just what you are working with: A few swipes with a SS brush really will make a difference. A freshly saw cut piece will weld wonderfully, and a quick brush and an acetone wipe if there is a concern of oil will guarantee you that a failure will be the weldor, not the base material.On stamped, or cast aluminum: You might need to use a grinder or a wire wheel to really cut through the skin, and get you to clean material. Cast bubbles, you will see crap in the weld. Be prepared to grind it out and weld a second time. Be sure to use filler the second time; don't try to fudge it. With regards to engines, covers, tranny's- You have to clean the cracks out, grind them, and clean them with acetone to get rid of the oil. It just makes life so much harder for you if you do not. Expect some misery, regardless. Oiled cast aluminum is NEVER as easy as you think it will be.For a grinder wheel- yes, the red flap disks will do you a good job. Just be sure to use new disks...... I prefer to use rough disks, like a 24,36 for baring the material. For thin sheet, I will go to a 50 grit. The main key is to not lay into the material really hard; you can burnish it with the flap disk, and leave plastic and chunk aluminum oxide from the disk; this is a major let down if it happens. If so, it's a lot more work with the SS brush to clean it, and more acetone.Everyone asks about old, half rotted aluminum. (Think boats...window frames, ladders.) The sky is the limit here. Throw it away and start over, or clean it with any variety of tools. Carbide die grinders, drill out old chalky holes (Be sure to drill out a hole if there is ANY chance of a steel screw or rivet chunk still in there.), flap disks for clearing chalky gunk off. Once a wheel is full of the chalky stuff, toss it. Get to shiny, and that is usually good enough. When you weld on it, you will always seem to see some floating junk. It's aluminum oxide, leftovers. Sometimes, it is down deep. Sometimes, it is drawn into the puddle, or pushed aside to the edge. A clean puddle with crap on it gives you an opportunity to grind it off the bead, and go over it again.ALUMINUM OXIDE: Different than anodizing, but similar problems. The oxide forms quickly. But in reality, a good, new piece of aluminum will have a decent amount of time before the oxide is thick enough to give you fits. Aluminum oxide melts at 3 times the temp of the base aluminum. Often asked: What does it look like, what does it weld like?? What you will see is a scaly crud on top of a puddle. Or, scaly gray crap and no puddle, though the amps are way up, and stuff is surely melted in there. Filler might not even flow in the 'mud puddle'. It has a nasty habit of jumping onto your tungsten... Stop, and the crud is now easier to focus on and remove. Maybe you get it all off, maybe not. Sometimes, it takes 2 or 3 tries. Too much heat and the blob will fall out, and you have a bigger issue..... Another sure fire key that you can SEE when welding, is a red halo. When you weld dirty on aluminum, and you might have brushed it fairly well, (Or so you thought...) you might see what looks like an oxy/ acet-like red glow. Almost like the aluminum is red hot like steel. That is a sure sign you still are working around the oxide. But most likely, the oxide is not enough to totally ruin your weld. Again, look closely at the weld and see if you need to clean with a brush and re-pass on it. Likely, you do.Anodized aluminum: Yes, you can weld right through it. Not the easiest thing to do, but it gets done by weldors all day long. Usually, a lot of filler is the key, to cause the burned anodize to float over the weld. It will lie broken, floating as it were on top and around the weld. Usually can not be cleaned off 100%. Silver paint..... problem solved.When cornered, you can weld aluminum much dirtier than is generally accepted. While not the desired program, sometimes it is what you are faced with. I suggest you try to intentionally weld some old, uncleaned aluminum to understand how it behaves, so you can learn what it takes to salvage a part. You will come away amazed at how much you can do when need be, and you will come to appreciate truly cleaned and prepped work. And don't be shy with the argon; I will weld as low as 12CFH on a small, clean part on a bench, but as high as 22-23CFH on dirty material. It does make a huge difference.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:one of the best fact based write ups i have read with no exaggeration about how the aluminum just has to be surgically clean.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:If the "aluminum" glows green it means the aluminum has a high zink content.Like repairs on weed eater engine cases. They make a special filler rod for that metal.AWS certified welding inspectorAWS certified welder
Reply:Very informative.  Thaks Rojo!!!BobI'm spending my Kids inheritance, I dont like him that much anyway!!!!!!Enuff tools to do the job, enough sense to use em.Anybody got a spare set of kidneys?  Trade?
Reply:Originally Posted by Donald BranscomIf the "aluminum" glows green it means the aluminum has a high zink content.Like repairs on weed eater engine cases. They make a special filler rod for that metal.