Optimization and evaluation of corrosion inhibitors for N80 steel in sulfamic acid solutions

Abstract

Sulfamic acid (SA) has a low acid-rock reaction rate and can be used for deep high-temperature acidizing. However, the inhibition effect of existing corrosion inhibitors at deep high temperatures is greatly reduced. Through experiments, it is found that corrosion inhibitors such as imidazoline (OAI), cinnamaldehyde (CA), C14 quaternary ammonium salt (C14-GN), and potassium iodide (KI) have good corrosion inhibition effect, the average corrosion inhibition rate can reach 99 %, and the corrosion rate is less than 2 g/m2 h. The experimental results show that the film formation of a single inhibitor is uneven and the pitting corrosion is serious. In contrast, the mixed-use of many kinds of inhibitors can effectively inhibit the pitting corrosion, and the corrosion rate is less than 1.6 g/m2 h. And it can effectively inhibit pitting corrosion. At 363 K, the corrosion inhibition rate is 99.9 % and the corrosion rate is 1.1 g/m2·h. Through the orthogonal test, it is concluded that the best inhibitor ratio is OAI: CA: C14-GN: KI = 3:3:3:2. The optimized inhibitor has the best synergistic effect, can play an important role at high temperature, make the film uniform and dense, and improve the corrosion inhibition effect of the solution of sulfamic acid with the investigated inhibitor.