In the previous two articles, we reviewed research progress in corrosion and protection technologies for marine environments. This installment focuses on another category of harsh conditions-extremely cold and high-altitude environments-and the corresponding corrosion and protection challenges.
Compared with common climatic conditions, extremely cold and high-altitude regions present much harsher environments. High-altitude areas are characterized by extreme temperature variations and high levels of radiation. Low temperatures and strong winds are also defining features of polar climates. For example, temperatures in the Arctic can drop as low as –60 °C, with wind speeds reaching up to 50 m/s. In addition, polar environments often involve ice debris and abrasive ice particles, which further exacerbate material degradation.
Organic anti-corrosion coatings used in extremely cold and high-altitude regions include traditional epoxy coatings, alkyd coatings, and polyurethane coatings. Acrylic resin topcoats also exhibit good weather resistance and superior gloss retention compared with epoxy and alkyd coatings, making them suitable for low-temperature applications. Although these environments are typically cold and dry, high ozone concentrations and strong ultraviolet radiation accelerate coating aging, leading to reduced adhesion, discoloration, chalking, and loss of gloss.
A major research focus in extremely cold environments is anti-icing technology, which aims to reduce ice adhesion on coating surfaces. Anti-icing coatings are generally classified into three categories: sacrificial coatings, icephobic coatings, and superhydrophobic coatings. Studies have shown that sol–gel-derived anti-icing slow-release coatings can significantly reduce ice adhesion strength. Silicone-based coatings have also demonstrated effective icephobic performance and are among the few commercially viable icephobic solutions. Most anti-icing coatings, however, are based on superhydrophobic surfaces. For instance, nanoscale fluorocarbon coatings have been shown to effectively delay ice formation.
Stress corrosion cracking of metal equipment and components is another critical challenge in polar and high-altitude corrosion protection. Stress corrosion typically occurs under relatively low stress and mildly corrosive media, yet failure can be sudden and highly destructive. In aircraft structures, components such as door frames, wing spars, and propeller hubs are particularly vulnerable to stress corrosion cracking, which can result in severe structural damage.
In high-altitude desert environments, sand and dust erosion pose serious wear problems for military equipment, systems, and airborne devices. Sand and gravel entrained in turbulent airflow generated by helicopter rotors can erode moving components, metal surfaces, and protective coatings. Fine dust particles can easily penetrate aircraft interiors, damaging precision metal structures and electronic systems. To protect aluminum alloy skins and other metal structures exposed to sand erosion, composite coating systems with elastic polyurethane topcoats have proven effective against abrasive wear. In addition, laser-cladded copper-based and nickel-based alloy coatings, known for their high hardness and excellent wear resistance, are used to delay wear-related failures in components such as artillery recoil mechanism rings.
