float switch gunk

[gettinthere]

What is this on my bilge pump float switch bracket?




The bracket is aluminum. It sits in a small pocket that is usually dry, only gets rain water when it rains hard. The white stuff is soft, like vaseline. The pocket it sits in is fiberglass. There are no wires in this pocket other than the wires to the float switch. No gunk on the switch or the wires, just the aluminum bracket.

 

[OPossumTX]

I don't know what it is, but I have seen it on aluminum before. I made an aluminum out-flow spout for my wife's koi pond filter and it would grow lumps of slime that looked just like that. Brush it off and you will find a pitted surface where it was if it is like what I saw.

 

[Chris Patterson]

I was having this problem with a fresh water tank sending unit, and the consensus from the "yard gurus" was electrolysis. Maybe it's bleeding through the switch.

 

[rgranger]

I'm going to guess it is an aluminum hydroxide or carbonate of some kind [Al(OH)4]-. The counter ion (cation) is probably sodium or potassium. If you can clean it up good and paint it with an epoxy paint, you might have some luck keeping it off.

Aluminum hydroxide is used as a flocculation agent in water purification. You add it to the water, it forms a gelatinous compound that is supposed to cling to all of the microscopic particles and settles to the bottom of the tank.

Although the formula might make you think that [Al(OH)4]- is formed by reaction with a base, that is not the case. The aluminum "grabs" the hydroxides from the water, thus releasing protons. So actually your water around this bracket is probably slightly acidic. Adding a little vinegar might help push the equilibrium back in the direction you want. Just a guess.