Monitoring of the Chemical Attack Produced on SA 533 GrA Steel in Complexing Evironment at High Temperatures

Abstract

SA 533 GrA steel is used in the building of vessels for heat exchangers. In the maintenance of these equipments, chemical cleanings are frequently done in order to keep their efficiency in the heat transfer. In these cleaning processes, complexing agents are usually employed. Between the components of this steel, Mn and S are found in the form of small nuclei of MnS. These points constitute zones more sensitive to any type of attack, either physical (stress) or chemical (localized corrosion, pitting). In this paper, we study by Electrochemical Noise Analysis (ENA) the chemical attacks produced on this steel in conditions of a real chemical cleaning. The complexing agent employed is the ammonium salt of ethylendiamintetraacetic acid at pH 8. By analysing electrochemical current noise it is intended to know what type of attack (localized or generalised) is produced on the steel during the cleaning process, and the influence of the concentration of complexing agent and working temperature on these attacks.