The surface color of stainless steel heat exchange tubes is not fixed and is closely related to the material, production process, and surface treatment method.
The surface of a normal stainless steel heat exchange tube should present a silver white metallic luster, which is its natural color. High quality heat exchange tubes usually have a bright and uniform color, and reflect clear light.
The differences in different materials are manifested as:
304 stainless steel: silver white with a slight light yellow tone, high gloss after polishing.
316/316L stainless steel: pure silver, with a colder color due to the presence of molybdenum element.
Plastic coating treatment: Some products may be coated with white (northern insulation) or red/blue (southern hot and cold water labeling).
The influence of different surface treatment processes on color:
Mirror polishing: high reflective silver white
Bright like a mirror, commonly found in high-end equipment.
Acid washing treatment: uniform silver white color
The surface passivation film is intact and has strong corrosion resistance.
Sandblasting treatment: matte silver white
No strong reflection, delicate texture.
Chemical coloring: multiple colors (gold/brown/purple, etc.)
Control the color through the thickness of the oxide film.
Normal stainless steel heat exchange tubes should present a uniform silver white metallic luster, and the specific color tone may vary slightly depending on the material and process. When the surface appears noticeably dull, discolored, or speckled, it may indicate a quality issue or the need for maintenance.