According to statistics, the steel equipment and materials scrapped due to metal rust each year is equivalent to about 30% of the steel output. The annual loss caused by metal rust in China can reach more than 100 billion. Today we will identify the state of rust of various metals. The characteristics of metal corrosion depend on the type of metal and the environment in which it is exposed. Generally, there are corrosion holes, color or gloss changes, and bulky and loose products.
1 Corrosion characteristics of steel and cast iron
When starting to rust, the metal surface is dark, light rust is dark gray, and further development will become brown or brown yellow, and serious brown or brown scars or even rust pits. After scraping away the corrosion products, the bottom is dark gray with irregular edges.
Color of corrosion products:
Fe (OH) 3: yellow; Fe3O4: black; FeO (OH): brown; Fe2O3: red; FeS: black; FeCl3: dark brown; FeCl2: dark green
2 Steel parts treated with bluish (oxidized) and phosphating
It is usually a yellow-brown rust layer, and some are spot-like and spot-like. The state of the corrosion products is the same as that of ordinary steel and cast iron. Because the steel surface is blue or gray after being blued and phosphated, the color of the corrosion products is deepened.
3 Copper and copper alloys
The corrosion of copper is green, and there are also orange red or brown. The rust of aluminum bronze can be a thin layer of white, dark green or black. In severe cases, it shows spots or layered protrusions. After removing the green rust products, there are pits at the bottom. The corrosion of lead bronze is sometimes white, and the corrosion of brass is sometimes white, dark yellow, green or black.
Copper corrosion product color:
CuO: black; CuS: black; Cu2O: orange-red; CuCl2: green; Cu (OH) 2 · CuCO3: green
