I took it to a metal fabrication shop to be cut open, cleaned and inspected. At that time we discussed the possibility of having a new one built. Once it had been opened up and cleaned I was told the +40 year old tank was as good as the day it was built so I don't know what the life expectancy of monel tanks should be. I know that other Alberg 35 owners in the Yahoo group have replaced their water tanks. I can only guess that they were damaged somehow.
My tanks are unpainted and show small green flecks on the surface. I'm guessing that may be some of the copper in the alloy but I really don't know. Stainless steel doesn't usually look like that. As you know metal isn't my medium.