**5.1 Drilling fluid inhibitor**

As the high concentration of Cl<sup>−</sup> in the oil field sewage, and also the role of CO2, H2S, dissolved oxygen, oil stain and miscellaneous, it results the serious pitting problems. At present, organic amine, organic polyol phosphate complex, imidazoline, and their derivatives and long carbon chain amide carboxylate are well used in this field.
