brianblock
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Does it weld ok? Any particular prep or techniques?
- Thread starter brianblock
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Jim Davey
R H Davey Welding Supplies Ltd
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Not really, you need to sand off the anodised layer first. If you are re-anodising the material afterwards be careful with your choice of filler material as there canbe issues with adhesion and discolouration of the anodising.
See here:
We have commercial 380 aluminum alloy, die cast into aluminum wiper arm heads, which are sulfuric acid anodized for paint adhesion (electrodeposited epoxy primer) and for corrosion protection (scribed salt spray). In the finished anodized parts we see mottled brownish areas in the dark uniform gray anodized finish. What are these areas? Die lubricants? Chemical segregation? Microstructure variation?
Alloy 380 is a high-silicon alloy (about 8 percent). The solubility of silicon in aluminum is about 1.5 percent. When the casting cools, silicon precipitates out and forms these gray mottled areas. Silicon does not anodize, so the adhesion around these areas is likely to be poor. To minimize this problem, the surface finisher should pretreat the casting in a nitric acid/ammonium bifluoride solution under well-ventilated conditions. Doing so will effectively dissolve much of the surface silicon and thereby enrich the surface with anodizable aluminum.
See here:
We have commercial 380 aluminum alloy, die cast into aluminum wiper arm heads, which are sulfuric acid anodized for paint adhesion (electrodeposited epoxy primer) and for corrosion protection (scribed salt spray). In the finished anodized parts we see mottled brownish areas in the dark uniform gray anodized finish. What are these areas? Die lubricants? Chemical segregation? Microstructure variation?
Alloy 380 is a high-silicon alloy (about 8 percent). The solubility of silicon in aluminum is about 1.5 percent. When the casting cools, silicon precipitates out and forms these gray mottled areas. Silicon does not anodize, so the adhesion around these areas is likely to be poor. To minimize this problem, the surface finisher should pretreat the casting in a nitric acid/ammonium bifluoride solution under well-ventilated conditions. Doing so will effectively dissolve much of the surface silicon and thereby enrich the surface with anodizable aluminum.
brianblock
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Ok thanks Jim, think I'll pass on this one
Unless you are welding some sort of die casting its unlikely to be 380 Aluminium so all that wouldnt apply.
Normal anodised Ally is simply treated to create an oxide layer that is appealing to the eye. It will oxidise naturally but may not be as pretty and would certainly not be coloured as some anodised layers are.
Really if you wire brush first (new st st brush) and use AC TIG with a lot of cleaning on you should be OK. Oh and a sharp tungsten.
Normal anodised Ally is simply treated to create an oxide layer that is appealing to the eye. It will oxidise naturally but may not be as pretty and would certainly not be coloured as some anodised layers are.
Really if you wire brush first (new st st brush) and use AC TIG with a lot of cleaning on you should be OK. Oh and a sharp tungsten.
rich the mechanic
Member
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I would like to add that anodised alloy is less electrically conductive (look at a Maglite the cap has bare alloy to allow a good conection) and anodising is done in sulfuric acid and heating/melting it can give off fumes the older it is the less it is noticeable.
AFC Anodising
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If you need any help with anodising related problems or questions, please contact AFC Anodising and we will be happy to help.
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craigthewelder
officially certified
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I've seen a video on you tube about this. The guy calls the technique he uses punch welding but it looks like a variation of tig pulse. He welds some tube that has been clear anodized, i'm not sure the colored anodizing would be any different.
PhillipM
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I need some help, can you give me the address for Mansfield anodisers?
At least they don't spam the forums...
