Reason for Corrosion in Finned Tube Heat Exchanger Tube

Reason for Corrosion in Finned Tube Heat Exchanger Tube

Finned tube heat exchanger in the petroleum, chemical, light industry, pharmaceutical, energy and other industrial production are widely used, after a long time of use, the tube will inevitably appear corrosion, which has a close relationship with the water impurity, atmospheric contamination of the water, the condition of the inner wall of the tube as well as the size of the water flow rate and other factors.

Due to the presence of scaling attachments (iron oxide, calcium salt deposits, sludge, etc.) on the inner wall of the pipe, localized corrosion and pitting corrosion often occurs in the pipe, the main reasons are as follows:

First, the water chamber side of the tube plate surface corrosion

Finned tube heat exchanger is located in the water chamber side of the tube plate surface, especially around the surface of the tube will also produce galvanic corrosion, this corrosion trace is patchy.

Second, the water side of the inner wall of the tube local erosion

When containing dirt, air, cold water (or cooling water) flow rapidly through the metal tube, will break through the tube on the inner surface of a layer of corrosion-resistant protective film. In the tube protective film stripped surface, due to the metal ion concentration difference, the formation of anodic (metal ions less parts) and cathodic (metal ions more parts) of the electrochemical corrosion, resulting in such corrosion of the tube surface will be presented on the fish scale pit concave and with small spots.

Third, the water side of the inner wall of the tube pitting and pore corrosion

Finned tube heat exchanger tube water side of the corrosion is in the case of uneven coverage of scale or other attachments. For copper and its alloys, when the surface of the inner wall of the tube is attached to the porous sludge, mud and sand, it will cause another electrochemical corrosion of the oxygen concentration difference battery. For example, when copper ions are contained in cold or cooling water, a battery can be generated so that copper ions are plated on iron and produce pitting and pore corrosion, i.e., the copper plating phenomenon.