A friend who is an engineer for a recreational vehicle manufacturer calls you and describes corrosion at the interface between the Type 321 stainless steel walls and the Type 347 stainless steel weld metal in a 15-gallon cylindrical tank for potable water. Wall thickness is 0.30 in., and the water is often liberally laced with chlorine for sanitation. What do you tell your friend? Is this a good design? What are the possible causes of the corrosion? There is no opportunity to examine the tank