Whether the metal frame of a three-tier dining car with stainless steel panels requires additional rust protection depends on a comprehensive consideration of the stainless steel's inherent properties, the car's intended use, and the frame's machining details. To extend its service life in humid environments, additional rust protection is generally recommended. The core of stainless steel's basic rust resistance lies in the chromium it contains, which forms a dense protective chromium oxide film on its surface. This film isolates air and moisture from direct contact with the metal substrate, thereby slowing corrosion. However, in actual use, the metal frame of a three-tier dining car encounters more than just moisture; it may also be accompanied by oil, food residue, and detergent residue, common in dining environments. These substances can damage the chromium oxide film. For example, acidic detergents can dissolve the film, while oil adheres to the surface, hindering its self-repair. This exposes the frame to corrosive environments, leading to the gradual development of rust spots or corrosion.
Particular attention should be paid to weak points in the metal frame's machining, such as welds, screw connections, and bends. During welding, high temperatures can cause uneven distribution of chromium in certain areas, reducing the rust resistance and creating "chromium-depleted zones." During screw connections, friction between metals can damage the oxide film on the contact surfaces, trapping moisture and dirt in crevices and causing crevice corrosion. Bends, where stress is concentrated during processing, can also cause microcracks in the oxide film, creating corrosion entry points. Even if stainless steel is used, these areas, relying solely on their oxide film, are unlikely to withstand long-term humid environments. Without additional rust prevention treatment, these areas can easily become the starting point for frame corrosion, compromising the structural stability and service life of the entire three-tier dining car.
To extend the lifespan, additional rust prevention treatment can provide more comprehensive protection for the metal frame, and it must comply with safety standards for restaurant environments. Common additional rust prevention methods include surface passivation, which chemically strengthens the thickness and density of the chromium oxide protective film, enhancing its corrosion resistance. This treatment does not produce harmful substances and is suitable for food contact environments. Alternatively, a food-grade anti-corrosion coating, such as epoxy resin or polytetrafluoroethylene, can be sprayed on the frame surface. These coatings form a physical barrier that not only isolates moisture and oil, but also withstands the temperature fluctuations common in food service environments. The coating itself is non-toxic and odorless, posing no food safety risks. For vulnerable areas such as welds and screws, localized electroplating treatments such as galvanizing or chrome plating can be applied. This provides a more corrosion-resistant metal layer, specifically addressing rust prevention in these vulnerable areas.
Additional rust prevention treatments are not permanent; routine maintenance is required to maximize the lifespan. For example, after each use, wipe the frame surface clean of moisture and oil to prevent long-term residue. Regularly inspect welds and joints. If any coating damage or localized rust is found, recoat or repair it promptly. Even so, basic additional rust prevention is still a prerequisite. If you rely solely on routine maintenance without additional rust prevention, once the oxide film is damaged, the corrosion rate will be much faster than the maintenance, making it difficult to fundamentally solve the rust problem in humid environments. In summary, while the metal frame of a three-tier dining car with stainless steel panels has basic rust resistance, in a humid and polluted dining environment, additional rust prevention can effectively compensate for the inherent weaknesses of the material, establishing a more comprehensive anti-corrosion system, significantly extending the service life of the three-tier dining car. It also ensures the long-term structural stability of the frame and avoids safety hazards caused by rust.
