In-situ measurement of electrochemical activity related to filiform corrosion in organic coated steel by scanning vibrating electrode technique and scanning micropotentiometry.

A new approach to studying the mechanism of filiform corrosion in organic coated steel based on the scanning vibrating electrode technique (SVET) and micropotentiometry (potentiometric SECM) is presented. The electrochemical activity of the process under the coating is evaluated by mapping the ionic current densities emanating from some artificial defects made in specific locations of the filament identifiable thanks to the transparency of the coating. In addition, antimony tips are employed to investigate the pH changes associated to the different corrosion reactions at the metal-paint interface. Local pH levels associated to anodic and cathodic regions are determined along the filament. [Display omitted] • Anodic and cathodic areas of filiform corrosion on organic-coated steel were identified by SVET. • The activity in the head confined into the "V-shape" morphology resulted anodic and the entire length of the tail cathodic. • Scanning micropotentiometry with an antimony microelectrode allowed local pH distributions in the filament to be measured. [ABSTRACT FROM AUTHOR]