Laboratory Investigation of Water-Side Scale And Corrosion in the Presence Of High Process-Side Temperatures

Abstract

Abstract A laboratory method of testing water-side corrosion and scale deposition in the presence of high process side temperatures has been developed. Two types of specimens are used: (1) a hairpin of ¼ inch seamless steel tubing mounted on a pipe plug and inserted in the circulating water system, and (2) a miniature heat exchanger made of ½ inch seamless tubing and standard pipe parts. In studies on corrosion rates, and on calcium phosphate scale deposition under conditions of 130 F water temperature and 350–395 F hot-side temperatures, it was shown that corrosion rates may be increased up to 8 times over the rates on immersed coupons at 130 F. A possible method of calculating water-side skin temperatures is indicated. It was shown that the use of polyphosphate treatments, at residual levels high enough to give corrosion protection, leads to the deposition of calcium phosphate scale. The use of chromate in combination treatments reduces the amount of this scale deposited, and also appears to reduce the amount of carbonate scale. 4.6.1