Volume 37, Issue 4

Austenitic stainless steels possess an excellent balance of strength and ductility along with the high ability to further raise their strength during cold deformation (CD). Corrosion resistance of austenitic stainless steels (SSs) is affected by cold deformation because passive films on the surface of steels are expected to be modified. A low level of CD enhances the surface diffusion, which results in the formation of a stable passive film leading to an increase in the corrosion resistance in neutral chloride solutions. The chromium content in the passive film on a deformed steel surface is usually richer, with a higher Cr/Fe ratio than that formed on annealed steels. A higher chromium content makes surface films more stable, which improves the corrosion resistance. However, severe CD results in the formation of strain-induced martensite phase and deformation twins, which decreases the localized corrosion resistance by increasing the number of active anodic sites on the surface. The corrosion resistance, especially the pitting resistance, in SSs is diminished with increasing volume fraction of the martensite. In this review, we highlighted the failure modes of corrosion of stainless steel implants, factors affecting corrosion, and effect of CD on mechanical properties and emphatically on the corrosion resistance of SSs for biomedical applications.

A systematic review of the literature about the corrosion of copper in intrauterine devices (IUDs) was conducted, an important topic of copper application that apparently may not be well known to a broad corrosion audience. Copper IUDs (Cu-IUDs) are one of the most widely used contraceptive methods around the world, particularly in China, India, and Latin America. The contraceptive method is based on the release of copper ions from a Cu-IUD. Copper ions enhance the inflammatory response in the uterine cavity and reach concentrations in the luminal fluids of the genital tract, which are toxic for spermatozoa and embryos. A description is made of the different types of Cu-IUD used, the traditional T-shaped device, copper nanoparticles inside a polymeric matrix, and other shapes. This review aims to discuss the main parameters affecting the efficiency of a Cu-IUD, the contraceptive mechanism, and the shape of the device. The high copper corrosion rate immediately after insertion in the uterus (“burst release”) is discussed, which presents values of the order of up to 296 μg/day, causing side effects such as bleeding and pain, with an exponential decay defining a steady-state plateau after 1–2 months of insertion with values of 40 μg/day for a 200 mm 2 Cu-IUD. This plateau is maintained over the life span of a Cu-IUD, in which the copper dissolution rate is as low as 2 μg/day for a Cu-IUD with indomethacin keeping up the contraceptive action mechanism, the concentration of copper that needs to be higher than 10 −6 mol/l.

Corrosion of metallic components represents a major issue in the aeronautical sector, giving rise to safety concerns and significant financial damages. Conversion coatings (CC) based on hexavalent chromium provide exceptional corrosion protection at relatively low cost. However, environmental issues and health concerns raised a growing interest in the development of alternative technologies. These must not only be cost effective and environmentally friendly but also provide corrosion resistance and adhesion performance comparable to Cr 6+ -based CCs. Simultaneously fulfilling all of these criteria is a difficult challenge, and an industrial application has so far only been achieved by a small number of systems. This review critically summarizes the recent scientific literature and patents for chromate-free CCs on aluminum alloys and tries to assess their potential regarding the highly demanding aerospace requirements. The bath composition and coating characteristics of the trivalent chromium process, rare earth chemical conversion coatings, transition metal oxyanion additives, Zr/Ti-based chemical conversion coatings, sol-gel coatings, and smart coatings providing stimulus-related inhibitor release are discussed. The advantages and disadvantages of the alternative technologies with regard to their practical implementation are debated, as the aeronautics industry is confronted with the necessity to move away from chromates in the near term.

Graphene-based coating is an emerging field that focuses on developing advanced coatings by exploiting new generation materials with superior properties. Researchers are striving to develop coatings that are cost-effective, easy to prepare and highly effective by integrating graphene with a wide range of suitable materials for surface protection applications. In this critical review, different types of high performing graphene-based polymer composite coatings have been described for anticorrosion application. An in-depth survey on methods of preparation, coating application techniques and their influence on the corrosion behavior of coatings is presented briefly. Newly developed strategies to enhance the protection efficiency of graphene-polymer matrix coatings are also covered concisely. The authors hope that this review will assist prospective academicians and researchers in developing novel highly efficient graphene-based anticorrosion composite coatings for industrial applications.