Assessment of Corrosion in Rebars by Impressed Current Technique

Abstract

In the construction industry, reinforced concrete has its own significance as the most used material due to its economic value, versatility and performance [1–3]. Today, durability has become a critical issue in the management of RC structures [4]. RC structures get deteriorated in many ways. Corrosion of steel rebar is the costliest mechanism which affects the service life and integrity of these structures [5, 6]. Bhaskaran et al. [7] studied economic loss in India due to corrosion during the period of 2011–12 using NBS input/output economic model. This study explained the capital loss as a result of corrosion sectorwise. In 2011–12, the cost of corrosion was $26.1 billion as the direct cost expenses which was 2.4% of Indian gross domestic product (GDP) and indirect expenses was $39.8 billion which was 3.6% of Indian GDP. According to NACE International IMPACT Study 2016, India’s total cost of corrosion is $70.3 billion, which is 4.2% of GDP of $1260 billion. As corrosion is an electrochemical process, it is to be noted that steel rebar in good quality of concrete is never going to corrode in the higher alkaline environment, even if the ample amount of oxygen and moisture is available required for the reactions to take place as a result of the formation of a passive layer (iron oxide film) [8, 9]. This film is protective in nature to steel rebar blocking the ion exchange between steel and concrete needed for corrosion, thereby decreasing its rate and preventing the damage to steel [6]. But there are some reasons which can cause the destruction of this passive layer such as the introduction of chlorides in the concrete environment or any cause due to which pH could be reduced in surrounding concrete such as carbonation or acid [2, 5, 6, 9]. The corrosion process has so many steps, but it starts in imperfect regions where there is higher or lower density in rebar’s crystal structures.