The Kelvin Probe Study on Initial Corrosion of Weathering Steel with NaCl Deposition
Scanning Kelvin Probe (SKP) combined with Scanning Electron Microscope (SEM) and Energy-Dispersive Spectrometer (EDS) analysis were used to study the corrosion behavior and electrochemical law of weathering steel Q450NQR1 deposited with NaCl particles at initial period of heat-damp test. The results showed that Q450NQR1 was severely attacked by Cl- for the reason that a low electric potential anode area was formed after a NaCl particle deliquesced rapidly. This anode area was corroded quickly, resulted in the appearance of rust spot, which led to a conductivity decline of the steel substrate and an increase of potential in the rust region. Moreover, tiny crack formed on the rust scale during the early stage and the galvanic couple between rust spot area possessing a high electric potential and metal substrate with a low electric potential were the two main reasons for the expansion of rust layer and the enhancement of corrosion.
Zhengyi Jiang, Jingtao Han and Xianghua Liu
C. F. Dong et al., "The Kelvin Probe Study on Initial Corrosion of Weathering Steel with NaCl Deposition", Advanced Materials Research, Vols. 152-153, pp. 493-499, 2011