Aluminum RIMS element bushing

while pondering ways to prevent rust in my RIMS heater (1.5" NPT stainless pipe fittings), i checked out the various 1.5" to 1" bushings available at mcmaster. it looks like they have a 356 aluminum alloy bushing. i don't know a heck of a lot about aluminum. anyone have any comments? good idea? bad idea?

thanks,

p.d.

You should not have rust in the SS pipe fittings.

bendavanza said:

You should not have rust in the SS pipe fittings.

Click to expand...

i don't. i want to keep the electric element base, which is mild steel, from rusting.

p.d.

What kind of element are you using? Seems kind of strange that you'd be having that much of a rust issue with it.

Yeah, but what is the aluminum going to do for you? Are you suggesting that it will modify the galvanic reaction?

Bobby_M said:

Yeah, but what is the aluminum going to do for you? Are you suggesting that it will modify the galvanic reaction?

Click to expand...

Seems like aluminum would act like a sacrificial anode... I think aluminum & magnesium are used as sacrificial anodes in hot water heaters.

I would think galvanic action would cause pitting but not rust.

I didn't mean that it would affect a galvanic reaction between the metals, but that the aluminum (or magnesium) would oxidize instead of the mild steel, preventing rust.

i was looking to use it as a sacrificial anode. i've got an electric HLT and rust formed on the element base just from sitting overnight in water. i can only guess the same thing is happening to the RIMS element, i just haven't taken it apart yet. putting an anode in an HLT is easy, and i was looking for something comparable to do for the RIMS heater.

from wikipedia (the "galvanic corrosion" entry):

"For example, consider a system is composed of 316 SS (a 300 series stainless steel; it is a very noble alloy meaning it is quite resistant to corrosion and has a high potential) and a mild steel (a very active metal with lower potential). The mild steel will corrode in the presence of an electrolyte such as salt water. If a sacrificial anode is used (such as a zinc alloy, aluminium alloy, or magnesium), these anodes will corrode, protecting the other metals."

FYI, people who use aluminum kettles or weldless fittings with aluminum locknuts would never see the base of their electric elements rust.

p.d.