Leaching Behavior and Corrosion Inhibition of a Rare Earth Carboxylate Incorporated Epoxy Coating System

Abstract

While paint coatings act as important barriers to corrosion, defects can lead to localized, rapid metal loss. The addition of corrosion inhibitors that are capable of leaching from a coating to protect the metal surface at a defect can prevent this type of corrosion. This work investigates the release and corrosion protection capabilities of two rare earth (RE) carboxylate inhibitors from an epoxy coating as an initial step to understanding their leaching behavior and interaction with the coating system. Leaching experiments were performed via inductively coupled plasma mass spectroscopy (ICP-MS) analyses of the solutions in which free-standing coatings loaded with varying concentrations of inhibitor compounds had been immersed. Inhibitor release from the epoxy coating was observed to be dependent on initial inhibitor concentration, inhibitor chemistry, and solution pH conditions. The coating systems with greater initial inhibitor loadings showed higher leaching rates, particularly in acidic environments. Following immersion, the absence of characteristic inhibitor peaks in the FTIR spectra of the coatings also confirmed leaching had taken place. Cross-sectional views of the coatings after exposure to the pH 1 environment presented a chloride infusion zone at the coating/solution interface where the inhibitor had leached out. The RE active inhibition provided by the leached RE carboxylate inhibitors was verified by exposure of a coating defect to a chloride contaminated environment.

Effect of Cerium Tartrate on the Corrosion Resistance of Epoxy Coating on Aluminum Alloy and Its Mechanism

“…After 7 d, the release rate decreases to 0.01 μg/(mL•d•cm 2 ) and then remains basically unchanged. This result is consistent with that in the literature [32]. Based on this, it can be inferred that cerium ions in the coating can also be released constantly towards the interface between the coating and…”

Analysis of inhibitory properties of Ce‐citrate as a green corrosion inhibitor of low alloy steel in neutral chloride solution

“…Relative effective corrosion inhibitors of steel in neutral chloride were obtained previously by combining the rare earth ions with different types of carboxylates. [19][20][21][22][23][24][25] These inhibitors can suppress both anodic and cathodic reactions (i.e., behave as mixed-type inhibitors) and provide much better corrosion protection than either the rare earth cations or the carboxylate anions. Among carboxylates, cinnamates (3-phenyl propionate and their different derivatives) have shown the best results as good ligands for rare earth cations.…”

“…Among carboxylates, cinnamates (3-phenyl propionate and their different derivatives) have shown the best results as good ligands for rare earth cations. [19][20][21][22][23][24][25] Other combinations of organic ligands such as salicylates, [18,26] acetylacetonate, [27] anthranilates, [28] octylsilanol, [29] and methyl-benzoyl-propanoate [30] with rare earth metals, primarily cerium cations, have been investigated. Recently, carboxylate inhibitors with different alkyl chain lengths as corrosion inhibitors of carbon steel have been tested.…”

“…Among carboxylates, cinnamates (3‐phenyl propionate and their different derivatives) have shown the best results as good ligands for rare earth cations. [ 19–25 ]…”

Li leaching from Li carbonate-primer: Transport pathway development from the scribe edge of a primer/topcoat system

“…In this study, the leaching into a scribe from the cut edge of a primer under a topcoat is examined in detail. There are several studies of protection within a scribe resulting in leaching of an inhibitor from a primer both for this Li 2 CO 3 -based coating system [4,5,7,9], as well as other inhibited systems [43][44][45][46][47][48]. However, much less has been done to characterize inhibitor depletion at the cut edge of the Li 2 CO 3 -based primer systems [49].…”