Abstract
Rotating corrosion tests of carbon steel were conducted in 40 natural fresh water samples collected from various regions. In these tests, five corrosion types were observed. That is, (1) No corrosion, (2) Pitting corrosion only, (3) Uniform corrosion, (4) Pitting in uniform corrosion and (5) Densely distributed localized corrosion.
A kind of Mahalanobis-Taguchi System (MTS) evaluation was applied to discriminate the corrosive water samples from non-corrosive ones. And also, MTS applicability to identify the dominating factors of carbon steel corrosion in freshwater environment was evaluated by determining optimum set of variables that gives minimum number of misjudgment.
From MTS evaluations using 5 or more water quality parameters, it is concluded that corrosive samples except for 3 particular samples that caused “Pitting Corrosion Only” can be discriminated from non-corrosive samples. And by using 7 proper variables considering interaction between water quality parameters, all the samples including 3 pitting samples mentioned above can be properly identified to be corrosive.
From the optimum set of variables, it is suggested that the interaction variable of [SO42-*M-alkalinity] and Silica-related variables may have major effect on the pitting corrosion of carbon steel in freshwater environment.
