Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

Abstract

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl−]/[OH−] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

A Review of Self‐Healing Concrete for Damage Management of Structures

“…A particular matter of concern for concrete is the decrease of alkalinity and depassivation of steel reinforcement caused by the ingress of chlorides and carbon dioxide (CO 2 ). Thus, recent advances in the development of microcapsules for chemical triggering have focused on the investigation of pH‐sensitive shell materials and chloride binding shell and cargo materials to target corrosion‐induced damage (Table ) . In particular, polystyrene and ethyl cellulose have been proposed as shell materials to envelop corrosion inhibiting/passivation agents through a physical extrusion process.…”

“…Thus, recent advances in the development of microcapsules for chemical triggering have focused on the investigation of pH‐sensitive shell materials and chloride binding shell and cargo materials to target corrosion‐induced damage (Table ) . In particular, polystyrene and ethyl cellulose have been proposed as shell materials to envelop corrosion inhibiting/passivation agents through a physical extrusion process. Conversely, using a similar mechanical process Xiong et al developed chloride ion–triggered microcapsules functionalizing sodium alginate with Ag + that can bind Cl − ions leading to collapse of the shell and release of the core material …”

Ion-triggered calcium hydroxide microcapsules for enhanced corrosion resistance of steel bars

“…Therefore, the effective encapsulation of corrosion inhibitor is required to control the release. There have been many reports on encapsulation of the corrosion inhibitors, where the release is triggered by pH [18][19][20] or crack. 21,22 Matsuda et al has synthesized pH-sensitive microcapsules with a shell composed of ester chains with the ability to be hydrolyzed in both alkaline and acidic, which can form oxide layer on the steel substrate.…”

Biogenic corrosion inhibitor on mild steel protection in concentrated HCl medium

“…A number of potential antifouling compounds have been isolated and searches for antifouling compounds, often include sponges, sea plants 12 , corals 13 , ascidians 14 , sea grasses 15 , sea stars 16 , bacteria 17 , fungi 18 , micro- and macroalgae (seaweed) 3 . Among the seaweed, Phaeophyceae or brown algae play an important role in the fouling of a wide range of immersed artificial substrata.…”