The corrosion rate of steel plates is significantly affected by environmental differences, with an average annual corrosion of about 0.1mm in still freshwater and over 0.25mm in industrial atmosphere. It is mainly influenced by factors such as medium composition, temperature, and flow rate.
Core data of corrosion rate
Static freshwater environment
The average corrosion rate is about 0.1mm/year, and the rust layer will hinder oxygen diffusion. The actual corrosion rate is lower than the theoretical value.
Industrial atmospheric environment
The annual corrosion rate can reach 0.2-0.25mm, and the presence of pollutants such as sulfides and nitrogen oxides can accelerate corrosion.
Seawater environment
Under full immersion conditions, the corrosion rate is about 0.5-1mm/year, and in the splash zone, it can reach 1-3mm/year due to the alternation of dry and wet conditions.
Key influencing factors
Environmental medium characteristics:
The concentration of dissolved oxygen is inversely proportional to the diffusion rate, and the supply of oxygen accelerates corrosion in high flow environments (such as pipeline walls).
When the concentration of chloride ions exceeds 200ppm, the risk of pitting corrosion in materials such as stainless steel significantly increases.
Temperature humidity interaction:
For every 10 ℃ increase in temperature, the corrosion rate increases by about 30%, but after exceeding 80 ℃, the oxygen solubility decreases, leading to a decrease in rate.
When the relative humidity is above 70%, a continuous electrolytic liquid film forms on the metal surface, and the corrosion rate increases sharply.
Material characteristics:
After 180 days in a salt spray environment, the corrosion rate of Q355NH weathering steel remained stable at 0.03mm/year, significantly better than that of ordinary carbon steel.
The annual corrosion rate of 40Cr steel in seawater can reach 0.5mm, which is higher than the 0.3mm of Q235 carbon steel
English