Cyclic oxidation tests in air with intermittent salt spraying have been performed to simulate the conditions of road salt (NaCl-CaCl2 ) enhanced corrosion in automotive exhaust systems. Tests were carried out at 600 and 700 degree C on three austenitic alloys, including two stainless steels currently employed for exhaust components (AISI 316 Ti and AISI 302B) and a higher nickel heat resisting alloy. The presence of salt causes internal corrosion, both along a regular front beneath an outer oxide scale and down alloy grain boundaries. An increase in temperature accelerates the corrosion rate and particularly enhances intergranular penetration. The results of micrographic and microanalytical investigations are in general agreement with an active oxidation mechanism in which Nax Clx vapour species, and not only chlorine, appear to play an important role. The regions directly affected are depleted in chromium and iron and enriched in nickel. Although internal oxidation of silicon is observed, a high silicon content (2%) does not necessarily ensure effective protection against this type of attack.
Simulation of road salt corrosion in austenitic alloys for automotive exhaust systems
Materials at High Temperatures ; 20 , 4 ; 561-571
2003
11 Seiten, 10 Quellen
Aufsatz (Zeitschrift)
Englisch
Korrosion , Auspuffanlage , Natriumchlorid , Spritzen , austenitischer nichtrostender Stahl , Nickel , Superlegierung , Korngrenze , Oxidation , Kühlung , austenitische Legierung , Salzkorrosion , Straßenverkehr , Calciumchlorid , Automobilbau , Abgasanlage , Umweltsimulation , Korrosionsgeschwindigkeit
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