For a boat on salt water, corrosion is an omnipresent demon.
Even inside. This is the spout on our galley sink which is piped to a saltwater foot pump. And to the cooling water discharge from our 12V refrigeration system, meaning that it has saltwater flowing out of it whenever the refrigeration compressor is running, as a telltail. Look closely at the inside of the right-hand bend... yup, the aluminum has corroded thru. I don't understand this... aluminum is supposed to be reasonably proof against saltwater. The pipe is clamped to the sink in a plastic fixture, and is connected below the sink via vinyl tubing... ruling out galvanic corrosion. The entire refrigeration system is 12V, so stray 110V current cannot be an issue. The compressor is powered by an external motor thru a V-belt.
The motor and compressor are mounted on the same metal plate, and there are some pressure switches to control the motor mounted on the compressor.
Is that enough to cause stray current corrosion, tho there is no direct connection between the refrigeration unit and the aluminum tubing except via the saltwater itself?
Or is the corrosion simply the result of flowing saltwater washing away the protective oxide layer on the inside of the aluminum tubing? I am very interested in what the net.wisdom has to say about this...
Regardless, this is the second spout that I have installed there, and they have gotten ridiculously expensive. I am not planning to buy a third one.
|Two pieces of 7/16" stainless tubing|
OK, a Plan B is needed.
It is also possible to prevent collapse/kinking if the tubing is filled solidly with something incompressible. Apparently some people have used ice (fill with water; freeze), but I was concerned that I'd never get the tubing bent before the ice started to melt. This is where Wood's metal comes in.
|This is Wood's metal - it is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. It melts at 158°F|
|Wood's metal foundry|
|Homemade bending jig|
|Recovering the Wood's metal|
And since our galley sink has two of these spouts (one for salt water and one for fresh water, foot-pumped from the tanks), I made another spout. Gotta be symmetrical, don't you know.
(Clever camera angle conceals dirty dishes in the sink)