Breakdown of organic coatings in corrosive environments examined by scanning kelvin probe and scanning acoustic microscopy

Reddy, B. S. R.; Doherty, M.; Sykes, J.M.

doi:10.1016/j.electacta.2004.01.055

Cited by 56 publications

(20 citation statements)

References 10 publications

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“…However, when the steel is not passivated, the cathodic reaction and the corrosion processes on the steel surface results in a significant electrostatic potential difference between the anode and the cathode on corroding systems [51,52]. The electrochemical potential of the system, φ , is governed by Poisson's equation where σ is the charge density and e the permittivity of the electrolyte solution at the coating-steel interface [53].…”

mentioning

confidence: 99%

Influence of substrate topography on cathodic delamination of anticorrosive coatings

Sörensen

Kiil

Dam‐Johansen

et al. 2009

Progress in Organic Coatings

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The cathodic delamination of a commercial TiO 2 pigmented epoxy coating on abrasive cleaned cold rolled steel has been investigated. The rate of delamination was found to depend on interfacial transport from the artificial defect to the delamination front and thereby the substrate topography, whereas the coating thickness had little influence. The presence of a significant potential gradient between the anode and the cathode and the dependency of the delamination rate on the tortuosity of the steel surface suggests that cathodic delamination is controlled by migration of cations from the defect to the delamination front. This means that abrasive blasting, to some extent, can be applied to control and minimize the observed rate of cathodic delamination. The lifetime of the species causing disbondment suggested that sodium hydroxide or potassium hydroxide and not peroxide species or radicals are the causative agents at free corrosion potential (i.e. without impressed current).

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mentioning

confidence: 99%

Influence of substrate topography on cathodic delamination of anticorrosive coatings

Sörensen

Kiil

Dam‐Johansen

et al. 2009

Progress in Organic Coatings

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“…However, it has been stated that before the blistering can begin, water or electrolyte solution has to have penetrated the base coat and reached the substrate, so that a local loss of adhesion and disbonding can start [11]. Blister formation is assumed to take place in "weak spots" [25], that are presumably present due to manufacturing, but the exact reason why blisters form where they form is still under debate [1].…”

Section: Dependence Of Damage Mechanisms On Coating Layer Structurementioning

confidence: 99%

“…The facilitated transport of ions in an electrical field gradient [2,3] might be such a process. It has been shown by Reddy and Sykes [25,26] that after cathodic reduction of rust at a defect the site "switches", becoming anodic and the cathodic region advances outward with new anodic sites developing in front of it. The authors state that around the defect easier pathways for currents of ions can develop due to the adhesion loss, thereby making high local currents underneath the coating possible [25,26].…”

Section: Fig 7: Measured Expansion Of the Migration Fronts For Samplmentioning

confidence: 99%

“…It has been shown by Reddy and Sykes [25,26] that after cathodic reduction of rust at a defect the site "switches", becoming anodic and the cathodic region advances outward with new anodic sites developing in front of it. The authors state that around the defect easier pathways for currents of ions can develop due to the adhesion loss, thereby making high local currents underneath the coating possible [25,26]. The potential gradients that result from the cyclic cathode/anode switches combined with the easier pathways could be responsible for the fast migration that was detected in our sample.…”

Section: Fig 7: Measured Expansion Of the Migration Fronts For Samplmentioning

confidence: 99%

“…removal of delaminated coating, measuring the rusted area underneath [3,8]). More advanced methods, based on electrical potential, electrical impedance or acoustic properties of the coating are Scanning Kelvin Probe (SKP) [25 -27], Electrochemical Impedance Spectroscopy (EIS) [6,27,28] and Scanning Acoustic Microscopy (SAM) [25,26,29], respectively. However, a combination of different methods can provide complementary information [13,30,31].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of delamination mechanisms in polymer coatings by scanning acoustic microscopy

Alig¹,

Bargmann²,

Oehler³

et al. 2010

J. Phys. D: Appl. Phys.

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Scanning acoustic microscopy (SAM) was used to investigate disbonding, delamination and blister formation in polymer coatings for different layer structures and initial defect depths during exposure to a corrosive environment. The time evolution of disbonding and blister initiation and their growth was investigated by analysing the SAM images exposure to an electrolyte solution (Harrison solution). From investigations of a model system of coatings on steel substrates, it was possible to differentiate between water and/or ion transport (i) through the coating and (ii) along the coating-steel interface. For samples without clear coat randomly distributed blisters appeared at the coating-steel interface after exposure to the electrolyte solution, irrespective of the location of initial defects. The random distribution of growing blisters is related to diffusion of water and/or ions through the coating and "nucleation" at weak points of the substrate or within the polymer. For samples with clear coat a propagating migration front along the coating-steel interface of 3-4 µm height -starting from initial defects -was detected. The linear propagation of this front cannot be explained by Fickian diffusion. Therefore, it is discussed in terms of an accelerated diffusion or crack growth kinetics. Since blistering starts only at sites, where the migration front has passed, the presence of a thin water layer at the coating-steel interface, the loss of adhesion and the following corrosive processes are prerequisites for the nucleation of blisters. The blister growth shows a square-root time dependence which was related to a diffusion controlled transport mechanism.

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Characterizing Inhomogeneity and Localized Corrosion on Coated Electrode Surfaces

Tan¹

2012

Heterogeneous Electrode Processes and Localized Corrosion

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Breakdown of organic coatings in corrosive environments examined by scanning kelvin probe and scanning acoustic microscopy

Cited by 56 publications

References 10 publications

Influence of substrate topography on cathodic delamination of anticorrosive coatings

Influence of substrate topography on cathodic delamination of anticorrosive coatings

Investigation of delamination mechanisms in polymer coatings by scanning acoustic microscopy

Characterizing Inhomogeneity and Localized Corrosion on Coated Electrode Surfaces

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