A revisit to solution-processed zirconia and its stabilized derivatives as protective coatings for base-stainless steel

Stainless steel (SS) is a well-known engineering material which is predominantly used in multitudinous applications; however, the disquieting entity is its deteriorative nature triggered by the corrosion in biological, chemical, and high-temperature surroundings. Zirconia is a noteworthy material because of its remarkable mechanical, thermal, and biocompatible properties. To further improve the properties, the high-temperature phases of zirconia are stabilized at room temperature. Zirconia and its stabilized derivates are favored candidates as protective coatings for SS. They offer high resistance, allow them to perform in corrosive, sensitive environments, and augment the longevity, serviceability of SS. Deposition of zirconia/stabilized-zirconia (Z/s-Z) coatings is accomplished using vapor-phase methods, which are capital-intensive; they comprise high vacuum and processing time, confined space, and more energy consumption, resulting in fabrication cost maximization. Alternatively, solution-phase deposition methods are advantageous, effortless, and capable of depositing on large-area substrates, promising to lessen fabrication costs and to enhance yield. Solution-phase methods, namely dip, spray, and spin coatings, have been investigated to produce effective, high-grade Z/s-Z coatings on SS. This review summarizes the utilized precursors, solvents, and process parameters for depositing Z/s-Z coatings on different types and grades of steel through mentioned solution-phase methods, respectively. The review emphasizes the researched potential applications of solution-phase processed Z/s-Z with a particular role as a protective coating on SS-based implants, surgical instruments preserving corrosion resistance, nontoxicity and biocompatibility in the body fluids. The review also highlights the defensive property of solution-phase processed Z/s-Z coatings to the underneath SS against corrosive chemical media (acids like H2SO4, HCl, HNO3; chlorides like NaCl and toxic gases like H2S, coal). The oxidation protection to the beneath SS by the mentioned coatings in aggressive high-temperature surroundings is also focused in the present review.