Originally Posted by Strider

This is not a true statement regarding the material selection. I have had many, many flawlessly operating (long term) evaporators made out of aluminum. Aluminum when properly passivated is more corrosion resistant than copper, while maintaining high heat transfer capability.

The problem is thus elsewhere, either in the design of the evaporator core, or in its manufacture.

Also, an evaporator core should only cost around $350 or so max, not $900...