Over-sink dish racks made of 304 stainless steel are used extensively in the humid environment of a kitchen, where their corrosion resistance directly determines their lifespan and hygiene safety. Surface treatment, as a core method to enhance corrosion resistance, involves altering the surface structure of stainless steel through physical, chemical, or composite techniques to form a dense protective layer, thereby isolating it from moisture, oil, and acidic substances. Common surface treatment processes include brushing, polishing, passivation, coating, and electropolishing. Each process enhances corrosion resistance through different mechanisms, adapting to the complex usage scenarios of a kitchen.
The brushing process creates uniform straight lines on the stainless steel surface through mechanical friction, giving the product a matte finish and reducing fingerprint residue and oil adhesion. The key to its enhanced corrosion resistance lies in the change in the surface microstructure—the brushing process creates countless tiny grooves on the surface. These grooves guide water droplets to flow in a specific direction, reducing the time water stains remain on the surface and thus lowering the risk of electrochemical corrosion. At the same time, the brushing process retains the metallic luster of stainless steel, balancing aesthetics and practicality, making it a common choice for kitchen over-sink dish racks.
Polishing, through multiple grinding processes, achieves a mirror-like finish on the stainless steel surface, its corrosion resistance stemming from the increased surface smoothness. A high-gloss surface reduces the adhesion area for moisture and dirt, making cleaning easier and preventing localized corrosion caused by dirt buildup. Furthermore, the extremely thin oxide layer formed during polishing further enhances surface density; however, over-polishing can damage the original passivation film, so process parameters must be strictly controlled to ensure a strong bond between the oxide layer and the substrate.
Passivation treatment is a key chemical process for improving the corrosion resistance of 304 stainless steel. By immersing an over-sink dish rack in an acidic passivation solution (such as nitric acid or citric acid solution), chromium on the stainless steel surface is oxidized to chromium trioxide (Cr₂O₃), forming a dense passivation film only a few nanometers thick. This film completely covers surface micro-defects, preventing the penetration of corrosive media such as oxygen, water molecules, and chloride ions. Passivated over-sink dish racks maintain their shine even in humid environments. Even if scratched, the passivation film regenerates through a self-healing mechanism, providing continuous protection.
Coating processes create a physical barrier by covering the stainless steel surface with a corrosion-resistant material, isolating it from corrosive media. Common coatings include epoxy resin, polytetrafluoroethylene (PTFE), and ceramic coatings. Epoxy resin coatings offer excellent adhesion and chemical resistance, effectively blocking moisture and acidic substances. PTFE coatings are known for their ultra-low coefficient of friction, reducing dirt adhesion and improving cleaning ease. Ceramic coatings, formed through high-temperature sintering, create a highly hard protective layer with excellent wear resistance, suitable for high-frequency use. The choice of coating process must comprehensively consider the characteristics of the kitchen environment, such as high temperature, high humidity, and frequent cleaning.
Electropolishing combines the advantages of electrochemical and mechanical polishing. Through the action of an electric current, the microscopic protrusions on the stainless steel surface are preferentially dissolved, forming a smooth, mirror-like surface. This process not only improves surface smoothness but also optimizes the uniformity of the passivation film. Electropolishing of over-sink dish racks results in a denser grain arrangement and significantly enhanced corrosion resistance, making them particularly suitable for kitchen environments with extremely high hygiene requirements. Furthermore, electropolishing eliminates surface stress concentration, reducing the risk of cracks caused by machining and extending product lifespan.
Combining multiple surface treatment processes can further improve the corrosion resistance of over-sink dish racks. For example, a brushed finish can create a flow-guiding texture, followed by passivation to generate a dense oxide film, and finally a thin epoxy resin coating, forming a multi-layered protective system of "physical flow guidance + chemical passivation + physical barrier." This composite process fully leverages the advantages of each technology to meet the challenges of multiple corrosive factors in the kitchen, such as moisture, oil, and acidic cleaning agents.
The surface treatment process for 304 stainless steel over-sink dish racks needs to be specifically designed based on the characteristics of the kitchen environment and usage requirements. While brushing, polishing, passivation, coating, and electropolishing enhance corrosion resistance through different mechanisms, the application of composite processes achieves a comprehensive performance improvement. Choosing the right surface treatment can not only extend the lifespan of over-sink dish racks, but also reduce cleaning and maintenance costs, providing a durable and hygienic storage solution for the kitchen.
