In industrial production and infrastructure construction, the corrosion loss of metal materials has always been an important factor affecting equipment service life and project safety. According to industry statistics, the direct economic losses caused by corrosion each year in China affect multiple core sectors, including energy, chemicals, municipal services, and marine engineering. As the scale of heavy equipment and coastal infrastructure continues to expand, operating conditions are becoming increasingly complex, making it difficult for procurement teams to accurately select from the diverse range of protective solutions. Reviewing the protective characteristics and applicable boundaries of different material systems can help users achieve the optimal balance between cost and service life.

Corrosion is essentially an electrochemical oxidation process in which metals react under the action of water, oxygen, and corrosive media. The core logic of various anti-corrosion technologies is the same: they delay the rate of substrate deterioration by disrupting the necessary conditions for corrosion reactions through physical isolation, potential control, or reaction inhibition. The protective principles, application processes, and applicable scenarios of different material solutions vary significantly, so comprehensive evaluation should be based on operating conditions and budget.

At present, mainstream protection approaches correspond to four types of material systems, each with its own performance and process priorities. Coating protection is the most widely used approach. It uses epoxy resin, polyurethane, fluorocarbon resin, and other materials as film-forming bases, combined with anti-rust fillers and functional additives. After surface derusting and multiple coating processes, including primer, intermediate, and top coats, a film is formed that isolates corrosive media through a dense barrier layer. Its advantages include flexible application and controllable costs, making it suitable for most normal-temperature and normal-pressure environments. However, its protective service life is highly affected by application quality, and local damage can easily accelerate the spread of corrosion. Electrochemical protection is divided into sacrificial anode protection and impressed current protection. The former uses zinc- or aluminum-based alloys as anode materials, allowing the anode to corrode preferentially through the principle of a galvanic cell and thereby protect the substrate. The latter uses an external DC power supply to make the component a cathode and inhibit oxidation reactions. It offers a long protection life and high stability and is suitable for long-term immersion in soil, seawater, and other environments, but requires a relatively high initial investment. Corrosion-resistant alloy modification improves protection capability through the material itself by adding elements such as chromium, nickel, and molybdenum to carbon steel to optimize passivation performance. Typical examples include stainless steel and weathering steel. These materials require no additional coating and have low maintenance costs, but their material and processing costs are far higher than those of ordinary carbon steel. Thermal metal spraying melts zinc or aluminum wire at high temperature and sprays it onto the surface of components, forming a metal protective layer that is then combined with a sealing coating. It provides a long protection cycle and is suitable for severe outdoor corrosion environments, but the application process is complex and requires highly skilled personnel.

The key factors affecting protection performance include the surface preparation grade, the degree of compatibility between the protection system and operating conditions, and the control of application temperature, humidity, and film thickness. Among these, failure to meet the required derusting grade and residual oil contamination or mill scale are the most common causes of premature protective-layer failure. For users purchasing anti-corrosion coatings, selection should begin with verifying third-party test data on salt-spray resistance, acid and alkali resistance, and other properties to confirm that the material performance matches their operating conditions. They should also evaluate the supplier's implementation cases in similar scenarios and its application service capabilities to avoid a disconnect between product specifications and on-site results.

The industry currently faces several common challenges: under complex, highly corrosive operating conditions, the actual protection life of a single technology is often shorter than the design expectation, while subsequent repair and maintenance costs remain high; on-site application quality fluctuates significantly due to differences in personnel skills, and uneven film thickness or missed coating can easily create weak points vulnerable to corrosion; tightening environmental regulations is also driving the replacement and upgrading of traditional solvent-based materials. In actual projects, combined solutions are often adopted. Ordinary factory steel structures commonly use epoxy primer combined with a polyurethane topcoat. Buried oil pipelines often use a polyethylene anti-corrosion layer combined with sacrificial anodes. Coastal bridges commonly adopt a composite system of thermal metal spraying and fluorocarbon sealing. In the future, protection solutions will develop toward environmental sustainability and composite systems. Water-based industrial coatings, composite systems integrating multiple technologies, and new self-healing materials will gradually become the mainstream direction of industry upgrading.