According to relevant heat exchanger design specifications, the pitting corrosion resistance of brazed stainless steel heat exchangers in chloride-containing media is a key indicator for selection. When the chloride ion concentration in the medium exceeds a certain range, the pitting potential of 304 stainless steel decreases significantly, while 316L, due to the addition of molybdenum, shows markedly improved pitting resistance. Therefore, design and selection personnel must first determine the chloride ion concentration in the medium.
Problem 1: If the chloride ion concentration is not fully evaluated and a BXS-30 brazed stainless steel heat exchanger made of 304 material is selected, pitting corrosion may form on the heat exchange surface, leading to leakage. Solution: It is recommended to require a complete medium analysis report during the selection stage, with focus on chloride ion content. If the concentration is high, 316L material should be preferred. At the same time, auxiliary measures such as increasing wall thickness corrosion allowance or adopting cathodic protection can be considered.
Problem 2: During equipment operation, chloride ions may locally increase due to concentration. Solution: Regularly test the medium composition, control operating temperature and flow rate, and avoid dead zones. During maintenance, deionized water should be used for flushing to avoid chloride ion residue. During shutdown, keep the equipment dry or under nitrogen protection.
In addition, the filler metal of the brazing process may also affect corrosion resistance, and it is necessary to ensure that the brazing material matches the base metal. Daily inspections should focus on whether there are rust spots or pinholes between the heat exchange plates, and address them promptly.
