dirty aluminum 2

[LynnMac]

I'm trying to weld an insert in an old aluminum boat. Coast Guard makes you weld 3 inches past new weld on bottom at round bar. My question is how to weld to the old trapped in dirt that I can't grind out. My weld must pass a dye pen test. I can't get a good weld where the dirt is trapped. Thanks for any help.

 

[gtaw]

You are right, you will not pass the PT test where you weld over dirty, oxidized aluminum. Clean it. Use a solvent to remove any material that is soluble and then remove the heavy soil and oxidation with a soft disk. Before you start welding, wire brush the surfaces with a stainless steel wire brush. Brush in one direction.

Keep in mind that most sanding disks and grinding wheels are composed of aluminum oxide which is exactly what you are trying to remove. Wire brushing with a hand brush should remove any oxide that remains from the soft sanding disk.

Aluminum oxidizes vey quickly, thus welding must be done within four hours of cleaning for best results.

Best regards - Al

 

[LynnMac]

Thanks, anyways Al, but the dirt is trapped where I can see it but i can't remove it.

 

[kingnero]

Cut out more...

 

[berkshire]

Try etching the Aluminum with caustic soda ( lye ) do not leave it on too long. Then clean the surface with distilled or de-ionised water.
If you are working underneath the boat, soak towels in the lye and press them up into place. Do not get any on you, wear rubber gloves and goggles.
When welding set the HF for max cleaning ,or as far as you dare to keep good penetration, watch out for salts boiling out of the aluminum as you weld.

 

[vanci]

I have used a very small tapered carbide burr with a pneumatic pencil grinder for removing material/ slag in hard to reach areas. Pick up a Dremel at the local hardware store.