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Stainless steel is susceptible to erosion and damage caused by Cl-, which is why there are many studies on the erosive effect of Cl- on stainless steel in oil and gas field environments. It is believed that the higher the Cl- content, the more negative the pitting potential and the more severe the pitting. However, research results in recent years have shown that there is a critical value for the effect of Cl- on the corrosion of stainless steel, mainly because Cl- has both promoting and inhibiting effects on pitting corrosion in stainless steel. On the one hand, Cl- has a small radius and strong penetrating power; it can adsorb onto the surface of stainless steel and then form FeCl2, an acid-strong and base-weak salt, with the Fe2+ generated as a result of corrosion. This leads to further acidification of the microenvironment on the metal surface, resulting in the formation of pitting nuclei that cause localized damage. Moreover, Cl- acts as a catalyst for these pitting nuclei, promoting the formation of pitting and accelerating the corrosion process. On the other hand, as the Cl- content increases, the solubility of substances such as H2S, CO2, and dissolved oxygen in water within oil and gas fields decreases, which inhibits the cathodic depolarization process associated with pitting corrosion in stainless steel and thus slows down the occurrence of pitting.