Summary for titanium grade for fasteners Discussion
Titanium grade for fasteners is the key question here: Ryan Lima asked which titanium bolts and nuts are acceptable for type III sulfuric anodizing, noting that titanium racks seem to conduct more evenly and won’t anodize like aluminum racks. He suspected commercially pure grades 1-4 might be suitable, but was unsure whether grade 5 would work because it is alloyed with aluminum. The reply, from an answerer speaking from book knowledge rather than hands-on experience, recommends CP grade 2 as a common fastener material and the safest choice to use. The answer also cautions that titanium is a poor conductor compared with copper, and grade 5 is even less conductive, so both conductivity and electrochemical resistance could be issues. The practical warning is that titanium bolts should not be relied on to carry current; any current flow through them is only incidental.
Q. I have been looking to increase my company’s inventory of titanium nuts and bolts for anodizing. We like using the titanium much more than aluminum racks since they won’t anodize and seem to conduct the electricity a lot more evenly. I’ve hit a snag though, in that I don’t know what grade of titanium is acceptable for type III sulfuric anodizing, since I don’t know what the bolts we already have are.
I am guessing that it must be the “CP” or pure grades, being 1, 2, 3 and 4. However, I am finding grade 5 all over the place and don’t know if that will work, or just get ruined since it is alloyed with aluminum.
Any help or knowledge on this topic is greatly appreciated.
Ryan Lima
– Keene, New Hampshire, United States
August 6, 2018
A. Hi Ryan. I am answering from book knowledge rather than any actual experience, but CP grade 2 is also a very common material for fasteners, so that’s what I’d use. Even chemically pure titanium carries very little current, maybe 3% of copper, and grade 5 carries maybe 1% of copper, so I imagine the conductivity as well as the electrochemical resistance of grade 5 alloy might be problems. Even still, you shouldn’t try to carry current with titanium bolts; I’m only referring to what incidentally can happen :-)
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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August 2018