About six hours ago, my 7 year old Siemens washing machine made a loud, explosive sound. I opened it up, unplugged the NTC sensor on the tub, and used an endoscope to inspect the inside. Apparently, the drum support, known as the 'spider' had disintegrated into pieces.
After some Googling, I found that modern machines often use aluminium for the spider arm. When water is present, the stainless steel drum and aluminium spider effectively form a galvanic cell. Electrochemical reactions cause the aluminium (lower electrode potential ) to corrode over time, eventually failing.
What are the possible options?
- Buy a Miele washing machine. Probably the best long-term solution, expensive
- Painting the spider or inserting nylon washers to isolate the metals, but these solutions aren't practical for machines with integrated tubs that are almost impossible to open.
- Add a sacrificial anode (like what's used in water heater tanks)—this is the first one I’m planning to try once I get a new washing machine. Stick a magnesium bar into the emergency drain area, fill the drum with soap and water, and then measure the potential difference between the magnesium and the drum. If it’s enough to create galvanic protection, I’ll try leaving the bar in place.
But for me even more interesting is the idea of using impressed current anodes, like they do in modern water heater systems. This involves applying a low voltage between the tank and a titanium anode. The titanium doesn’t corrode, but by making it the anode via external current, it protects the rest of the system.
In theory, maybe I could mount a mercury slip ring on the drum shaft and case and fix the slip ring to the drum via some soft material, like TPU? The drum could be biased as a cathode, and I can put the titanium bar somewhere others. I am not sure this would work in mechanically.
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