Hollow stainless steel: Low grade stainless steel will rust. The higher the chromium content of stainless steel, the less likely it is to rust.
304 solid stainless steel: 304 stainless steel contains 16% chromium, good stability, strong corrosion resistance, and will not rust even in long-term humid environments.
Alumina: The surface is easily corroded and easily oxidized. Easily flattened or bent,
Zinc alloy: Zinc alloy towel rack will not rust. But the quality is not as good as other materials, and it is easy to break.