Cleaning and welding cracked oily cast aluminum

Let me start with "I like working with aluminum"
Cast aluminum IMO is a total crap shoot as to whether it will weld or not. Best I can offer is to clean it as best you can with some kind of degreaser. Again not with brake cleaner! It will in my experience never come clean. As you weld the heat will draw the oils into it. I've cooked it in ovens used acetone,Mek, let it soak over night in whatever.
Cast aluminum is just porous. Mig or Tig it seems that you just do your best weld then grind out the bad weld created by the oil contamination and weld it again. Sometimes it takes 4 plus try's. sometimes only once. Or it can turn out to be just crap and turn into this balled up fuzz coated mess.
I won't offer a quote or guarantee on any cast. It always come with the statement that there may be nothing for them to came back and pick up.
DanO


Master of unfinished projects
 
I've rebuilt a number of old tools and car parts. The only sure way to get rid of the oil in the pores is HEAT and lots of it.
I've used hot water in a basement sink on smaller parts. Dollar stores have a detergent called "Awesome" (really) that is fantastic, but DON"T breathe the hot fumes.
On larger parts I've had good luck taking my parts to a transmission shop with a hot washer. If you can wait til they run a transmission through, they'll often do it for free.
 
I agree with what has been said but thought i would add one tip that has worked for me on cracks in aluminium castings. After cleaning the more than you think is needed by like three times and I agree grinding disks leave to much abrasive dust embedded in the surface, files are better. After cratering cracks and chasing cracks with base metal falling apart i start to run a tig pass on either side of the crack first as a sort of primer pass to get some fresh clean metel alloyed into the base metal this makes a thicker easier to weld joint if you can get to the back side weld it first and back gouge before weld the outside. On a valve cover i would probably do a multi pass build up discarding the ear making the whole repair out of weld and then reshaping and drilling the hole. some castings are much worse than other and I always start with the understanding that we may not get the desired result.

Bob
 
I boil oily aluminum parts in water and dawn dish washing liquid for an hr or so, let dry, and then bake in an oven at 300 deg for an hr, pull it out if you see oil repeat, until no sign of oil. Prep for weld clean with alcohol or aceatone. Weld . This works for me!! Hope it helps!!
 
I don't know about Cat equipment, but I have seen magnesium used for covers from time to time. Just throwing it out there.
A friend TIG welds motorcycle cases etc on vintage machines all the time and cleaning multiple times is the only way, so he says time and again.
Pierre
 
Rbeckett said:
Clean, clean, clean, and clean some more. Use hot steam or boiling water and a degreaser/ Once you get the item clean, bake it in the oven on low for a while to draw the remaining oil from inside the crack, Clean it some more. Use a dedicated aluminum only wheel to groove the crack, and use a dedicated stainless steel brush to clean the grooved out area. Tig weld the crack in multiple small passes with carefull grinding between each pass. This will eventually get you clean solid base metal that will form a leakproof weld. Cleaning is a major issue because the oil will continue to contaminate the site multiple times. Brake or motor cleaner releases a toxic vapor, so be extremely carefull if you use those products to avoid breathing any of the cloud that will come offf of the part. I generally do NOT use those chems, Dawn dishwashing dtetrgent and elbow grease works just as well. Hope this helps, If you need procedure settings PM me and I will be glad to help you set it up.

Bob
Click to expand...
I second all of this only I like a burr for gouging. Stay away from brake fluid. even when thought clean just a small amount in a pin hole can turn into enough gas to kill you, or scar your lungs bad. Boiling in water and dish soap works good. but in the end the first couple passes will likely have to be ground out do to oil coming out. Here is a video
http://www.bing.com/videos/search?q...&mid=62692FE9A55604F5C77C62692FE9A55604F5C77C
 
A thorough cleaning (I use lacquer thinner) and heat up with a torch to draw oils out and clean again. As smoothers have stated, depending on the base material quality, different end results. I just did a old corvette aluminum bell housing that worked great. I keep stainless wire brushes for aluminum only.

Be carful when heating with a torch. Use the appropriate size tip to prevent meltdown.
 
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