naimis
Contributor
I'm at the point where I'm ready to get the housing for my dive light and put it all together, but I have a few concerns...
Like most folks, I'm building a cannister light. But a cannister light has a lot of opportunities for leakage, with multiple penetrations with the cable, the lens and possibly the back of the light.
The penetrations into the head I'm only a little worried about, the coefficient of thermal expansion should be similar enough between the 6061 aluminum and the brass the gland is made out of, but PVC has a very different COE. PVC doesn't make a good threaded seal on a good day (I've built water rocket launchers and used threaded PVC and it never sealed very well, even with teflon tape).
Also, I've been concerned about the possibility of galvanic corrosion between the gland and the head, and contact welding as well. These can probably be addressed reasonably well by throwing some teflon tape on the threads. Has anyone out there addressed these issues yet, and if so, how?
I spoke with an engineer at the office about these issue and he didn't think that 6061 was a good alloy to be using for this application because it's not very corrosion resistant. He subsequently referred me to Online Materials Information Resource - MatWeb and McMaster-Carr (the latter I had already visited from following other related threads) to get information about various alloys.
I've also seen at least one person anodize his machined light head, but the same engineer indicated that we didn't really have any good shops here in Austin to do that.
So, in summary, what are people doing to address these issues?
1) contact welding / galvanic corrosion
2) differences in coefficients of thermal expansion
3) corrosion due to exposure to (salt) water
Like most folks, I'm building a cannister light. But a cannister light has a lot of opportunities for leakage, with multiple penetrations with the cable, the lens and possibly the back of the light.
The penetrations into the head I'm only a little worried about, the coefficient of thermal expansion should be similar enough between the 6061 aluminum and the brass the gland is made out of, but PVC has a very different COE. PVC doesn't make a good threaded seal on a good day (I've built water rocket launchers and used threaded PVC and it never sealed very well, even with teflon tape).
Also, I've been concerned about the possibility of galvanic corrosion between the gland and the head, and contact welding as well. These can probably be addressed reasonably well by throwing some teflon tape on the threads. Has anyone out there addressed these issues yet, and if so, how?
I spoke with an engineer at the office about these issue and he didn't think that 6061 was a good alloy to be using for this application because it's not very corrosion resistant. He subsequently referred me to Online Materials Information Resource - MatWeb and McMaster-Carr (the latter I had already visited from following other related threads) to get information about various alloys.
I've also seen at least one person anodize his machined light head, but the same engineer indicated that we didn't really have any good shops here in Austin to do that.
So, in summary, what are people doing to address these issues?
1) contact welding / galvanic corrosion
2) differences in coefficients of thermal expansion
3) corrosion due to exposure to (salt) water
