Corrosion resistance is a core performance indicator of a stainless steel vertical refrigerator, and the surface treatment process is a key factor in determining this performance. Different processes directly affect the refrigerator's corrosion resistance in humid, salty, or chemically contaminated environments by altering the surface composition, structure, or morphology, thereby affecting its service life and appearance stability.
Passivation treatment is a fundamental process for improving the corrosion resistance of stainless steel vertical refrigerators. Through chemical or electrochemical methods, a dense chromium oxide film is formed on the stainless steel surface, effectively shielding it from the intrusion of corrosive media such as oxygen, water vapor, and chloride ions. This process significantly improves the refrigerator's stability in coastal or high-humidity environments and is particularly suitable for areas exposed to moisture, such as doors and handles. The integrity of the passivation film depends on the treatment time and temperature. Improper process parameters can lead to a loose film layer, reducing its protective effectiveness.
Polishing improves surface finish by mechanically or chemically improving corrosion resistance, indirectly enhancing corrosion resistance. Mechanical polishing uses abrasive materials to remove surface defects and reduce stagnation points for corrosive media; electrolytic polishing uses electrochemical dissolution to smooth the surface, forming a uniform oxide film.
After polishing, the surface roughness of a stainless steel vertical refrigerator is reduced, allowing the water film to distribute more evenly, thereby reducing the risk of localized corrosion. However, it should be noted that over-polishing may damage the original passivation film, necessitating a subsequent passivation process to restore its protective properties. This step is particularly important for delicate components such as refrigerator door seals.
Sandblasting or brushing enhances corrosion resistance by modifying the surface topography. Sandblasting uses high-velocity sand particles to impact the surface, creating a uniform, uneven texture that increases surface area and improves coating adhesion. Brushing, on the other hand, uses mechanical friction to create straight or intersecting lines, giving the refrigerator a unique decorative effect. Both processes conceal machining marks, reduce stress concentration points, and mitigate pitting corrosion. However, a rough surface can accelerate the accumulation of dirt, requiring regular cleaning to maintain its protective effect. For stainless steel vertical refrigerators exposed to kitchen fumes for extended periods, applying an oil-repellent coating after sandblasting can significantly improve stain resistance.
Electroplating and electroless plating enhance surface protection by depositing a metal layer. Electroplating of metals such as chromium and nickel creates a hard, wear-resistant coating suitable for wear-prone areas such as refrigerator handles. Chemically plated nickel-phosphorus alloys, due to their uniformity and strong bonding, are widely used to protect complex structural components. These coatings not only isolate corrosive media but also protect the substrate through sacrificial anodes. However, strict control of coating thickness and porosity is required. Insufficient thickness can easily penetrate the coating, while excessive porosity can become a starting point for corrosion. Therefore, this process requires particular caution when applied to large-surface components such as refrigerator side panels.
Coatings are a cost-effective means of improving the corrosion resistance of stainless steel vertical refrigerators. Coatings such as epoxy resins and polyurethanes can completely cover the surface, forming a physical barrier and are particularly suitable for corrosion-prone areas such as welds. High-performance coatings also offer chemical and scratch resistance, extending the life of refrigerators in harsh environments. However, coating quality is highly dependent on application techniques. Incomplete surface pretreatment can lead to coating detachment, and insufficient curing temperature can cause pinhole defects. Therefore, coating treatment requires rigorous process control.
Ion nitriding improves surface hardness and corrosion resistance by incorporating nitrogen. After S-phase ion nitriding, austenitic stainless steel can achieve a surface hardness exceeding 800 HV, significantly enhancing its corrosion resistance. This makes it an ideal choice for high-load components such as refrigerator compressor supports. However, it should be noted that conventional ion nitriding can compromise corrosion resistance, requiring process optimization to ensure a balanced performance.
Different surface treatment processes enhance the corrosion resistance of stainless steel vertical refrigerators through their own mechanisms. In practice, the process combination should be selected based on the refrigerator's operating environment, cost budget, and appearance requirements. For example, passivation and coating may be preferred in coastal areas, while sandblasting and oil-repellent coating may be suitable for kitchen environments. This synergistic process can maximize the refrigerator's service life and ensure stable performance in complex environments.
