Evaluation of Atmospheric Corrosivity by ACM Technique

Abstract

The atmospheric corrosion has been shown to be an electrochemical process, the atmospheric corrosion behavior of Q235 stell evaluated with ACM (Atmospheric corrosion monitor) electrochemical technique was investigated in the study. The experimental results showed that there existed a close relation between electrochemical data and climatic parameters was confirmed. Taking into consideration accuracy and sensitivity of electrochemical technique, the ISO-standardized time of wetness (TOW) seems to be too conservative. SO2 seems to be more aggressive than chloride on metal corrosion in the early stage of atmospheric corrosion but the complexion reverses in the final stage of atmospheric corrosion. The ratio of corrosion rate from integration of ACM current to corrosion rate from weight loss of test specimens, that is, cell factor is fairly constant at the same test site but varied greatly between test sites. Based on constant cell factors and close relation between electrochemical data and climatic parameters in all test sites, ACM electrochemical technique can evaluate and classify the short-term atmospheric corrosivity as a substitute for gravimetric method, and the verification shows that atmospheric corrosivity classifications according to integration of ACM current and especially to cell factor coincide with the specifications of ISO Standard.

Corrosion Monitoring in Atmospheric Conditions: A Review

“…Cao et al determined a cell factor value by comparing the ACM data and the mass loss of simultaneously exposed coupons according to the equation [27]:…”

“…where ∆m ACM is weight loss obtained by integration of ACM current, and ∆m coupons is the weight loss of simultaneously exposed coupons. They reported the cell factor being almost constant over time at a single test site but different among test sites [27]. The average cell factor value was used for signal correction at one site.…”

Electrochemical investigation on atmospheric corrosion of carbon steel under different environmental parameters

“…Atmospheric corrosion has been shown to be an electrochemical phenomenon under thin electrolyte films, so it is reasonable to consider electrochemical techniques for studying the process (Chung and Kim, 2000; Mansfeld et al , 1986). In the past, and for many years, electrochemical techniques have been developed to study the corrosion behavior of the metals covered by thin electrolyte films, to produce an atmospheric corrosion monitor (ACM) (Mansfeld et al , 1986; González et al , 1990; Mansfeld and Kenkel, 1976; Walter, 1991a, b; Sun et al , 2010; Cao et al , 2009), Kelvin probe technique (Stratmann and Streckel, 1990; Tahara and Kodama, 2000; Frankel et al , 2007), electrochemical impedance spectroscopy (EIS) (Shitanda et al , 2009; Nishikata et al , 1995; Silverman, 1993; Li et al , 2010), electrochemical noise (EN) (Torres‐Mendoza et al , 2006; Leban et al , 2001; García‐Ochoa et al , 2008; Wu et al , 2005), etc. The present studies bring more profound understanding of atmospheric corrosion of metals under thin electrolyte films and explore some new ways of monitoring the process.…”