STUDY OF INTERACTION OF THE FORMED HIGH PRESSURE AND TEMPERATURE BOILERS INTERNAL SCALES ON THE CORROSION BEHAVIOUR OF CARBON STEEL TUBES

Abstract

In the study,the interaction reaction of carbon steel with the chlorides of chromium, nickel and j

j { sodium have been investigated.The metal-salt inte- f ]fraction reaction system lead to from self-contr- jf olling corrosion types. The carbon steel specimens I buried in the pure and dry chloride salts which are # individually compact under 10 Kg/cm at 350°C for j j two hours, EDXRF, SEM, O/P micro-scope, XRD, [ li A.A, micro-hardness and USV techniques to i l analyze and interpret the mechanistic steps of the lf corrosion process.The results of the three systems jj jf could be summarized in the following; jj t l a-Steel-Chromium Chloride. f Dissolution of carbon steel-CrCl,dry system is #; li passed in steps within the predominant temperature #i lj (350°C) reaction medium. At the early step, the j jf surface of the top layer of the compact CrCl, (dark j jj greenish color) is oxidized to be converted into j # CrCI(violet color) due to the small rise of tempe- f j rature range of the thermal stability. However, the # i$ underneeth layer is not converted yet. Though in it# $ the occurrence of oxygen the top layer surface of j # CrCl, is gradually vanished due to the variation of # #f sublimation state.The sublimated metastable of CrO #f #j is oxidized to form Cr,O, black stable precipitate. # $ This black oxide could be acting as anticorrosion j @ coating of carbon steel alloy specimen.