（1. Faculty of Materials Science and Engineering， Kunming University of Science and Technology， Kunming 650093， Yunnan， China 2. Institute for Special Steel， Central Iron and Steel Research Institute， Beijing 100081， China）
Abstract：439M ferritic stainless steel is widely used in automobile muffler of exhaust system and the pitting corrosion damage is the main failure form. The pitting corrosion test， the initiation pH of depassivation and micro-electrochemical test were applied to study the morphology of the pitting corrosion and inclusions combined with the analysis ofscanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS). Also the variation of inclusions was researched at the start of pitting corrosion occurrence. The results indicated that the pitting corrosion was found to be initiated at the interface between the round oxide inclusion complex and the matrix， while little pitting corrosion occurred arround the TiN inclusion. The composite oxide inclusions containing Ca-oxides part can be preferential dissolved when inclusions induced pitting corrosion. Finally， the model of the initiation process of the composite oxide inclusion-induced pitting corrosion in 439M ferritic stainless steel exposed to chloride ions environments was established.
A. Pardo, M.C. Merino, A.E. Coy, F. Viejo, R. Arrabal, E. Matykina, Pittingcorrosion behaviour of austenitic stainless steels combining effects of Mnand Mo additions, Corrossion Science, 2008,50:1796–1806.
[4]
A. Pardo, M.C. Merino, A.E. Coy, F. Viejo, R. Arrabal, E. Matykina, Pittingcorrosion behaviour of austenitic stainless steels combining effects of Mnand Mo additions, Corrossion Science, 2008,50:1796–1806.
[5]
A.S. Mikhailov, J.R. Scully, J.L. Hudson, Nonequilibrium collective phenomenain the onset of pitting corrosion. Surface Science, 2009,603:1912–1921.
[5]
A.S. Mikhailov, J.R. Scully, J.L. Hudson, Nonequilibrium collective phenomenain the onset of pitting corrosion. Surface Science, 2009,603:1912–1921.
[6]
K. Asami,K. Hashimoto. Importance of initial surface film in the degradation of stainless steels by atmospheric exposure. Corrossion Science, 2003,45:2263–2283.
[6]
K. Asami,K. Hashimoto. Importance of initial surface film in the degradation of stainless steels by atmospheric exposure. Corrossion Science, 2003,45:2263–2283.
[7]
C.O.A. Olsson, D. Landol. Passive films on stainless steels-chemistry, structureand growth. Electrochim. Acta 2003,48:1093–1104.
[7]
C.O.A. Olsson, D. Landol. Passive films on stainless steels-chemistry, structureand growth. Electrochim. Acta 2003,48:1093–1104.
[8]
W. Fredrikssona, S. Malmgrena, T. Gustafssona, M. Gorgoib, K. Edstr?ma. Fulldepth profile of passive films on 316L stainless steel based on high resolution HAXPES in combination with ARXPS, Appl. Surface Science,2012, 258:5790–5797.
[8]
W. Fredrikssona, S. Malmgrena, T. Gustafssona, M. Gorgoib, K. Edstr?ma. Fulldepth profile of passive films on 316L stainless steel based on high resolution HAXPES in combination with ARXPS, Appl. Surface Science,2012, 258:5790–5797.
[9]
Heon Young Ha,Chan Jin Park,Hyuk Sang Kwon.Efeects of non-metallic inclusions on the initiation of pitting corresion in 11% Cr ferritic stainless steel examined micro-droplet cell[J].Corrosion Science,2007,49:1266-1275.
[9]
Heon Young Ha,Chan Jin Park,Hyuk Sang Kwon.Efeects of non-metallic inclusions on the initiation of pitting corresion in 11% Cr ferritic stainless steel examined micro-droplet cell[J].Corrosion Science,2007,49:1266-1275.
[10]
V.vignal,R.Oltra and N.Mary.Advances in local electrochmical techniques for detecting pitting corrosion[J].Corrosion,2004,1-5.
[10]
V.vignal,R.Oltra and N.Mary.Advances in local electrochmical techniques for detecting pitting corrosion[J].Corrosion,2004,1-5.
[11]
Eric G.Webb,Richard C.Alkire.Pit initiation at single sulfide inclusions in stainless steel I.elctrochemical microcell measurements[J].The Electrochemical Society,2002,149(6):272-279.
[11]
Eric G.Webb,Richard C.Alkire.Pit initiation at single sulfide inclusions in stainless steel I.elctrochemical microcell measurements[J].The Electrochemical Society,2002,149(6):272-279.
[12]
T.L.Sudesh,L.Wijesinghe,D.J.Blackwood,Real time pit initiation studies onstainless steels: the effect of sulphide inclusions, Corrossion Sceince. 2007,49:1755–1764.
[12]
T.L.Sudesh,L.Wijesinghe,D.J.Blackwood,Real time pit initiation studies onstainless steels: the effect of sulphide inclusions, Corrossion Sceince. 2007,49:1755–1764.
[13]
王俊琴，刘云霞.铌在不锈钢中的应用[J].大型铸锻件，2004，2：51-53.
[13]
王俊琴，刘云霞.铌在不锈钢中的应用[J].大型铸锻件，2004，2：51-53.
[14]
Xu H,Xu L D,Zhang S J,Han Q.Scr Mater,2006,54:2191.
[14]
Xu H,Xu L D,Zhang S J,Han Q.Scr Mater,2006,54:2191.
Wranglen G. Active sulphide and pitting corrosion of carbon steels [A]. Proceeding of International Congress on Loca-lized Corrosion [C]. Williamburg va. USA, 1971.
[18]
Wranglen G. Active sulphide and pitting corrosion of carbon steels [A]. Proceeding of International Congress on Loca-lized Corrosion [C]. Williamburg va. USA, 1971.
2015, Vol. 50 
