Protective mechanisms occurring on zinc coated steel cut-edges in immersion conditions

Galvanic corrosion between zinc and carbon steel investigated by local electrochemical impedance spectroscopy

“…A model of galvanic corrosion occurring on a galvanized steel cut-edge couple in near neutral conditions was proposed. In the model, the galvanic coupling was supposed to occur in a uniform conductive medium, with oxygen as the only diffusing species [15][16][17]. Souto et al showed that SECM greatly enhances the information gathered on corrosion reactions by allowing the spatial distribution of pH to be imaged (quasi) simultaneously [18].…”

“…More recently, with the development of local electrochemical techniques, which allow local processes at a microscale to be investigated, the study of galvanic coupling, has known a renewed interest. For example, scanning vibrating electrode technique (SVET) and scanning electrochemical microscopy (SECM) have been used to study the galvanic coupling between zinc and steel (or iron) [13][14][15][16][17][18][19][20][21]. Simoes et al reported that the SVET and the SECM techniques provide complementary and consistent information on the local ionic fluxes and local reagents and products concentrations due to the cathodic and anodic reactions occurring above the zinc/iron surface during the galvanic coupling.…”

“…Furthermore, with the SECM, the concentrations in the aqueous phase can be estimated, thus providing in situ information as a function of immersion time [14]. Thebault et al used SVET to investigate the protective mechanisms occurring on zinc coated steel cut-edges in immersion conditions [15][16][17]. They reported that the current density measurements over the cut edge of galvanized steel had revealed three distinct kinetic regions: an anode localized over the zinc surface, a region of partial inhibition of the oxygen reduction and the cathodic area on the opposite side of the steel.…”

Review—On the Application of the Scanning Vibrating Electrode Technique (SVET) to Corrosion Research

“…For this reason the corrosion of cut edges of galvanized steel has been extensively studied with industrial and model samples. 39,[85][86][87][88][89][90][91][92][93][94][95][96][97][98] One of the studies using SVET described in the literature is presented in Fig. 7.…”

“…The "passive" behavior was attributed to a self-healing mechanism by the formation of an oxide film during the very early stages of the immersion when the cathodic and anodic current densities were at a maximum. [92][93][94][95] Painted metals.-The application of SVET to characterize the corrosion on painted metals has received great attention but its use is limited to systems with defects. If the coating is in perfect condition, corrosion is absent and no currents are there to be measured.…”