Electrochemical electrolyte spreading studies of the protective properties of ultra-thin films on zinc galvanized steel

• Published in: Surface & coatings technology Vol. 228; pp. 286 - 295
• Main Authors: Posner, R., Fink, N., Wolpers, M., Grundmeier, G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.08.2013; Elsevier
• Subjects: Accelerated corrosion testing; Applied sciences; Cathodic delamination; Conversion coating; Corrosion; Corrosion environments; Cross-disciplinary physics: materials science; rheology; Delaminating; Delamination; Electrochemical impedance spectroscopy; Electrolytes; Exact sciences and technology; Galvanized steels; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Production techniques; Reactive electrolyte spreading; Reduction (electrolytic); Spreading; Surface treatment; Surface treatments; Thin films; Zinc; Zinc galvanized steel; Zinc galvanized steel; Cathodic delamination; Conversion coating; Accelerated corrosion testing; Reactive electrolyte spreading; Galvanized steel; Surface treatments; Coatings; Thin films; Corrosion; Protective layer; Corrosion testing; Delamination
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2013.04.042

Reactive electrolyte spreading along the surfaces of different conversion films on zinc galvanized steel in humid air was monitored visually and with a height-regulated scanning Kelvin Probe. Electrochemical impedance spectroscopy and current density-potential curves revealed that decelerated spreading kinetics are connected with increasing pore resistances of the pre-treatment layers and decreasing oxygen reduction current densities in the electron transfer controlled potential region. After a few days the progress ranking of electrolyte spreading along uncoated conversion films reflected the progress tendencies of cathodic delamination observed on epoxy coated conversion layers after long-time exposure to the same corrosive environment. Such correlation was not discovered for pre-treatment films that do not provide relevant electrochemical barrier properties. The results suggest that oxygen reduction driven electrolyte wetting is an option for accelerated performance testing of anticorrosive ultra-thin films on metal substrates that can be subject to cathodic delamination. •Electrolyte spreading and cathodic delamination are similar on conversion coatings.•Interrelation of electrolyte spreading, barrier properties and oxygen reduction.•Electrolyte spreading kinetics can anticipate the progress of cathodic delamination.•Options for cost-efficient and accelerated corrosion testing are shown.