Microencapsulation of natural self-healing agent as corrosion coating

Abstract

Microencapsulation of natural self-healing agent is an emerging technology that would allow this particular material to protect and cover metal coating’s structural defects caused by extreme mechanical and chemical environments. A very common option for the protection of metal from corrosion is by coating their surfaces with any suitable coating substances but when damage occurs, this coating may be broken and becomes ineffective. Therefore, a possible improvement to this coating system is by incorporation with self-healing agents. This extra condition permits the damage to be healed instantaneously and this leads to the life extension of the metal as well as the whole structure. This paper presents the results of tung oil, linseed oil and sunflower oil as the potential self-healing agent. The optimization of sunflower oil as the self-healing agent was performed. The two parameters involved in this experiment were stirring speed and reaction time of agitation process. The microcapsules produced were then embedded with metal paint as a self-healing coating. The resulting coating was applied to a prototype of coolant container (mild steel material) and subjected to a number of tests including corrosion measurement testing. The microcapsules which were stirred at 500 rpm stirring speed with 4 hours reaction time produced the microcapsule size of 0.566 µm. The reaction time influenced the agglomerated morphology of the shell of the microcapsules. The agglomerated microcapsules shell generates well incorporation of microcapsules in metal paint. This finding revealed that the coatings with microcapsules exhibited excellent corrosion healing while significantly increasing the lifespan of the coolant container as compared with normal metal coatings without microcapsules when subjected to a controlled corrosive environment. It can be concluded that microcapsules based on a natural self-healing agent could be very promising coating materials, especially for metal coating applications.