In the past ten years, there has been a progressive development in corrosion monitoring technology [1–12]. Initial approaches to evaluate the performance of steam generator (SG) alloys were based on mass-loss coupons and polarization resistance measurements of probes in SG environments or aggressive water chemistries. Corrosion rates and mechanisms were characterized and quantified with data obtained from metallurgical examination of test specimens. Several of these earlier autoclave tests were conducted over a number of years with inconclusive results. Recent interest has focused on the application of modern electrochemical techniques [6,7], such as current and potential electrochemical noise, for greater sensitivity in the evaluation of localized and general corrosion behavior.
This paper reviews the progress to date of a multidisciplinary study to investigate the feasibility of electrochemical techniques to evaluate steam generator materials. The primary techniques investigated were electrochemical current noise measurement (ECNM), zero resistance ammetry (ZRA), and electrochemical potential noise measurement (EPNM). Several applications, including monitoring localized and general corrosion of steam generator tubes and other material combinations, with and without crevices, are discussed. Future developments and their potential impact on plant reliability, integrity, and safety programs are reviewed.