A focused review on smart carriers tailored for corrosion protection: Developments, applications, and challenges

Abstract

Steel-made infrastructures have been expanding at an incredible rate worldwide and are critical for the expansion and operation of countless industries. Steel is susceptible to corrosion failures, particularly in aggressive environments, and requires surface protection and effective corrosion management to avoid failures. Corrosion failures are a serious and costly problem. In the Middle East region, the direct costs of corrosion are estimated at around 5% of the gross domestic profit (GDP). The indirect costs are much higher and often unpredictable. Given the economic importance of steel-made infrastructures, its corrosion creates major problems for many industries, namely the oil and gas industry, and is responsible for very high operational expenditures (OPEX). Consequently, the coating industry is under constant pressure, as they need to supply the best coatings to the end-users, ensuring adequate corrosion protection and compliance with the environmental requirements. Corrosion protective coatings are the prime choice for steel protection and are, nowadays, the focus of considerable attention and intense research effort. The reason is that there is an extraordinary increase in environmental consciousness that has been accompanied by new legislation and regulations that concern people's safety, assets sustainability, reliability, and protection of the environment. This scenario poses an enormous challenge to the industry: how to comply with these requirements while keeping competitive solutions and sustainable operations and maintenance costs. Smart multifunctional coatings are providing a viable solution to address the corrosion challenges in a wide range of industries due to their promising self-healing properties. The targeted properties of smart multifunctional coatings are deeply influenced by the type of functionalities, pigments (including smart carriers), inhibitors, self-healing agents, the matrix itself, and the synthesis route. A large variety of anti-corrosion pigments have been designed and used as smart carriers to encapsulate/load various types of inhibitors and/or self-healing agents. In this review, we summarized the recent developments made in the field of pigments used as smart carriers for corrosion protection of steel in numerous industrial applications. Various nanocarriers, also referred to as smart nanocarriers, have been reported comprising of inorganic, organic, and hybrid scaffolds and used as additives in coatings for corrosion protection of different materials. This review also includes various characterization techniques employed to evaluate the self-healing performance of coatings modified with smart carriers. Besides, commendable advances, there is still the need for progress in designing novel smart carriers compatible with different coatings matrices and able to be loaded with various chemical species to enhance the corrosion protection ability and self-healing performance. It is, therefore, essential to review the earliest developments made so far for a better understanding of the existing strategies. A concise overview on this topic will provide a robust scientific background and will serve as a baseline to synthesize future novel smart carriers for developing anti-corrosion coatings with improved self-healing performance. Overall, such systems are expected to serve as facilitators for better corrosion management of coated steel parts.