汽车SCR系统用不锈钢的冷凝液腐蚀行为研究

运用600 ℃废气氧化与80 ℃冷凝液浸泡方法研究了柴油机SCR系统用441和304两种不锈钢的冷凝液腐蚀行为。结果表明：经有/无尿素的废气氧化后,441不锈钢在冷凝液中的腐蚀均处于钝化状态,而304不锈钢的腐蚀均处于活化状态;阳极极化曲线测量后,441不锈钢表面形成了点蚀坑,304不锈钢部分表面区域有明显的晶间腐蚀特征,氧化环境中引入尿素对两种不锈钢的前述局部腐蚀都具有增强作用。

Condensates Induced Corrosion of Stainless Steels for Automotive SCR System

The corrosion behavior of type 304 and 441 stainless steels was investigated in a simulated environment of diesel exhaust selective catalytic reduction (SCR) system by using a two step tests, i.e. first the steels were suffered from hot exhaust gas oxidation at 600 ℃ for 100 h and then immersed in a simulated condensates solution at 80 ℃to reveal their electrochemical corrosion characteristics. The results indicate that, after oxidation at 600 ℃ in the exhaust gases with and without addition of urea respectively, 441 stainless steel shows passive corrosion state in the condensates solution, whereas 304 stainless steel is in active corrosion state. After polarization curve measurements, some pits formed on 441 stainless steel surface, and intergranular corrosion feature was observed on parts of 304 stainless steel surface. After the oxidation in hot exhaust gas with addition of urea, the aforementioned localized corrosion for both 304 and 441 stainless steels can be accelerated during the subsequent corrosion in the condensates solution.