Further investigationn indicates that the white substance is some kind of salt which is the result of corrosion. The spotted areas are seriously and deeply pitted under the salt deposits. Cutting access holes indicates that the corrosion is mostly on the welded areas.Comment from a welder suggests that the reason for the other spots of corrosion is that the areas where these spots occured is probably where the welding material spattered. I wonder if proper welding techniques and materials were used. 1.Any welders out there with thoughts on this theory?I am aware of the deletorious health consequences of aluminum consumption IE: suspected connection to alzheimers disease. I am considering some kind of non-metallic replacement tank. 2. Has anyone done this?This boat is a 37.5 and there is a nearly useless storage area forward of the water tank. I am considering putting the new water tank further forward into the very front of the bow and using the space left under the v-berth for drawers or some other more useful storage. 3. Any ideas on this modification?4. How will moving the tank forward affect the balance or handling of the boat?