Delamination mechanisms under the co-existence of alternating stress and corrosion

In a new work, the delamination behavior of a defective coating in the coexistence of alternating stress and electrochemical corrosion was studied in a novel experimental setup in which the electrochemical measurement and fatigue test could be conducted simultaneously.

Alternating stress and corrosion show a synergistic effect on coating delamination Image source: fancycrave1 - Pixabay (symbol image).

The coating delamination occurring in the conditions where alternating stress and corrosion co-exist threatens the coating integrity and operating life. The electrochemical impedance spectroscopy and scanning electron microscope coupled with X-ray energy dispersive spectroscopy were employed to analyse the degree and mechanism of coating delamination, as well as the ABAQUS software was used to simulate the stress distribution on the substrate surface. The results show that in a corrosive environment, the rate of the coating delamination increases dramatically once the alternating stress is applied. The coating delamination occurs first at the stress concentration and expands rapidly to the surrounding area.

Synergistic effect on coating delamination

The interfacial adhesion of the coating-substrate is weakened by the joint action from accumulated fatigue and local alkalisation. Accumulated fatigue and local alkalization are resulted from alternating stress and corrosion, respectively. As a result, the coating delamination occurs rapidly. Meanwhile, alternating stress and corrosion show a synergistic effect on coating delamination, i.e., alternating stress accelerates corrosion process, while corrosion exacerbates the mechanical damage of alternating stress. The study has been published in Progress in Organic Coatings, Volume 180, July 2023.

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