Theoretical and experimental study of microcell and macrocell corrosion in patch repair

Patch repair is commonly used to rectify localized corrosion induced damage in concrete structures. However, inadequate durability in patch repair systems caused by new corrosion attack is prevalent. From the prevailing understanding, the mechanism is attributed to macrocell corrosion formed between repaired area (called patch) and its adjacent unrepaired area (called substrate), and thereby ensuring electrochemical compatibility between the two areas is deemed to be the key element to reduce the corrosion risk and thus to achieve a successful repair. This paper examined the corrosion mechanism and the concept of compatibility in patch repair systems from fundamental electrochemical principles and experimental verification. It was illustrated that both macrocell and microcell corrosion mechanisms could play significant roles, and the total corrosion could be underestimated if the latter is overlooked. Although theincompatibility serves as the driving force for the macrocell corrosion, in light of corrosion kinetics, it was shown that the corrosion magnitude depends more on the individual corrosion kinetics of the anode or cathode.On utilise ordinairement la technique du rapi\ue9\ue7age pour rem\ue9dier aux dommages localis\ue9s caus\ue9s par la corrosion dans les structures de b\ue9ton. Toutefois, il est courant que les syst\ue8mes de rapi\ue9\ue7age soient inad\ue9quatement durables en raison de l?attaque de la nouvelle corrosion. Il est g\ue9n\ue9ralement admis que ce m\ue9canisme est attribuable \ue0 la corrosion macrocellulaire form\ue9e entre la partie r\ue9par\ue9e (d\ue9sign\ue9e rapi\ue9\ue7age) et les parties non r\ue9par\ue9es adjacentes (d\ue9sign\ue9es substrats). Par cons\ue9quent, on consid\ue8re que la compatibilit\ue9 \ue9lectrochimique entre les deux zones doit \ueatre l?\ue9l\ue9ment cl\ue9 \ue0 atteindre pour r\ue9duire le risque de corrosion et ainsi obtenir des r\ue9fections durables. Dans ce document, on examine le m\ue9canisme de corrosion et la notion de compatibilit\ue9 des syst\ue8mes de rapi\ue9\ue7age, \ue0 partir des principes \ue9lectrochimiques fondamentaux et de la v\ue9rification exp\ue9rimentale. On a fait ressortir que les m\ue9canismes de la corrosion tant macrocellulaire que microcellulaire pouvaient jouer des r\uf4les consid\ue9rables, et qu?\ue0 d\ue9faut de tenir compte de la corrosion microcellulaire, il risque d?y avoir sous-estimation de la corrosion totale. Bien que l?incompatibilit\ue9 soit l?\ue9l\ue9ment moteur de la corrosion macrocellulaire, \ue0 la lumi\ue8re de la cin\ue9tique de la corrosion, il a \ue9t\ue9 d\ue9montr\ue9 que l?ampleur de celle-ci d\ue9pend davantage de la cin\ue9tique de la corrosion individuelle de l?anode ou de la cathode.Peer reviewed: YesNRC publication: Ye