新型汽车排气系统用铁素体不锈钢的冷凝液腐蚀研究

 铁素体不锈钢中Cr元素对其耐腐蚀性能起着非常重要的作用。本文采用实验室冷凝液腐蚀实验方法，对一系列汽车排气系统用铁素体不锈钢在实验室模拟冷凝液中的腐蚀性能进行了研究。所有钢种经过10周期的实验室冷凝液腐蚀实验后，研究结果表明：Cr当量高于17%的铁素体不锈钢与含17%Cr的铁素体不锈钢耐实验室冷凝液腐蚀性能相当，且平均腐蚀失重量均小于6g/m2，平均最大腐蚀深度均小于0.03mm。在此实验结果的基础上，对新开发的439M型铁素体不锈钢和409L型铁素体不锈钢进一步开展5周期、10周期、20周期的实验室冷凝液腐蚀实验，并使用极值分析方法对三种周期冷凝液腐蚀实验后样品的最大点蚀深度进行统计分析，研究结果表明，新开发的439M型铁素体不锈钢的预测寿命是409L的1.6倍。

Condensate Corrosion Behavior of A New Style Ferritic Stainless Steel Used in Automotive Exhaust System

Cr plays a very important role in the corrosion resistance of ferritic stainless steels. The corrosion resistance of a series of ferritic stainless steels used in automotive exhaust system was evaluated by a condensate corrosion test. As a result, the condensate corrosion resistance of ferritic stainless steels contained more than 17% Cr was almost the same with the ones contained 17% Cr after ten periods of the condensate corrosion test. Moreover, the average corrosion lost weight was lower than 6g/m2 and the average maximum corrosion depth was less than 0.03mm for the two types of ferritic stainless steels. According to the test result, the new developed type 439M ferritic stainless steel and type 409L stainless steel were studied in the condensate corrosion test for 5 periods, 10 periods and 20 periods separately. The maximum pitting depths on the samples’ surface after various period corrosion tests were calculated by extreme value analysis to evaluate the maximum pitting depth of the whole muffler. The result indicates that the forecasted longevity of 439M ferritic stainless steel is 1.6 times of 409L stainless steel’s.