Hello all, I am in the planning stages of replacing our old 3 stage iron phosphate pretreatment washer with a new 7 stage iron / zinc phosphate washer. My question concerns fabrication material. Mild steel is out of the question as it will rust out like our current washer. That leaves Stainless and Composites (NewPac Finishing). Has anybody had experience with composite washers? I was told, by a stainless washer manufacturer, that the composite washers have expansion / contraction issues which cause the seams to leak over time. Has anybody experienced this problem? I do not want to base my decision on what one manufacturer tells me about another manufactures product. Thank you all.