Corrosion protection mechanisms of carbon nanotube and zinc-rich epoxy primers on carbon steel in simulated concrete pore solutions in the presence of chloride ions

Abstract

This study investigates the electrochemical characterization of carbon nanotube and zincrich epoxy primers (CNT-ZRPs) on carbon steel in simulated concrete pore (SCP) solutions in the presence of chloride ions. The mechanistic performance of CNT-ZRPs was characterized by adding different zinc content. The electrochemical results indicated a dominant barrier protection effect for the coating with 60 wt% Zn while there was a mixed corrosion protection mechanism for the coating with 70 wt% Zn and a dominant cathodic protection mechanism for coatings with

Magnesium Nanocomposite Coatings for Protection of a Lightweight Al Alloy: Modes of Corrosion Protection, Mechanisms of Failure

“…OCP measurements provide an effective means of evaluating the extent of cathodic protection afforded by sacrificial coatings . Figure contrasts the evolution of the OCP for 17 and 50 wt% Mg/PEI nanocomposite coatings with that of the bare AA7075 substrate (ca.…”

“…The rapid cathodic polarization of the alloy substrate by the Mg nanocrystals is quite distinctive from the behavior observed for Zn‐rich coatings, wherein initially the OCP is more anodic than that of steel substrate and then fluctuates before reaching a stable mixed potential value. The observed fluctuation in the latter case can be ascribed to the presence of native ZnO, which must be dissolved in order to activate the Zn particles . Mg nanocrystals also exhibit a native passivation layer; however, the passivation layer appears to be readily dissolved upon penetration of the electrolyte within the coating as a result of the high reactivity of magnesium in the presence of ionic species.…”

Effect of graphene on the electrochemical protection of zinc‐rich coatings

“…During the earlier stage, the zinc particles provide cathodic protection through galvanic contact with the steel . It is usually reported that the zinc dust content in dry coating must be more than 90 wt% in order to establish a reliable percolation path . Once the zinc particles corrode, its contact to the steel substrate will gradually be lost.…”

“…Therefore, researches have been performed to develop ZRC with long‐time cathodic protection by partial substitution of zinc pigments with conductive fillers. Carbon nanotubes (CNTs) were added to the ZRC for improving the electrical contact between the particles . It was found that the CNTs could provide higher electrical conductivity with a lower zinc concentration.…”

Performance of a Magnesium-Rich Primer on Pretreated AA2024-T351 in Full Immersion: a Galvanic Throwing Power Investigation Using a Scanning Vibrating Electrode Technique

“…This approach has been well established and widely reported in the design of zinc-rich primers for use on various steels. [18][19][20][21][22][23][24] The galvanic protection potential is usually dictated by mixed potential theory and mediated by various electrical/ionic resistances between the anode and cathode such as: polymer barrier properties of the MgRP, pretreatment resistances, electrolyte chemistry, electrolyte thickness and geometry, and anode/cathode ratio. 9,10 Barrier protection is afforded by the MgRP itself and also the pretreatment layer.…”