Soutenance de thèse de Hazem MUBARAK

09/12/2016

Degradation of 304L stainless steel in acidic solutions: Influence of stress state on the passivation kinetics, and cracking crystallography and mechanics.


A multidisciplinary experimental approach of electrochemical and mechanical techniques was employed to study the corrosion of different stress states of 304L stainless steel in acidic electrolytes (0.5-5 M H2SO4) with and without chloride additives. Stress corrosion cracking (SCC) conditions were applied to evidence cracking crystallographical and propagation aspects.

Scanning electron microscopy of SCC revealed clear traces of successive slipping planes and consequent dissolutions on the crack facets, and nonlinear crack propagation kinetics. A method was proposed to access cracking crystallography using electron back scattered diffraction. It demonstrated {111} and {110} preferential cracking planes in proportion of about  75% and 25% respectively, which supports  recent SCC models such as corrosion enhanced localized plasticity. The profiles of (applied/residual) stress evolution measured by X-ray diffraction before and after SCC were used as an introduction to develop a micro-mechanical cracking model.

 

During optimized potentiodynamic corrosion tests, elemental dissolution rates and total current transients were measured by combining electrochemical flow cell and downstream solution analysis by inductively coupled plasma atomic emission spectroscopy. The results were used to separate the current portion spent on passive film formation from the total current.  The high field ion conduction model was upgraded to calculate the constructed passive film thickness and passivation rate. A slight difference on the passive film growth kinetics and thickness was detected as an effect of 280 MPa tensile stress compared to unstressed samples.

 

Keywords: Stress corrosion cracking, Stainless steel, 304L, Passivation , Acidic corrosion of stainless steel, Metallic dissolution, Scanning electron microscopy, Electron backscatter diffraction,  X-ray diffraction, Cracking planes, Crystallography, Micro-mechanics, Simulation.

 

Directeurs de thèse : Kevin OGLE, Chimie ParisTech, Laurent BARRALLIER, Arts et Métiers ParisTech

Co-encadrants : Polina VOLOVICH, Chimie ParisTech, Sébastien JEGOU, Arts et Métiers ParisTech

 

Jury

Pr. Vincent JI, Univ. Paris Sud

Pr. Vincent VIGNAL, Univ. de Bourgogne

Pr. Halina KRAVIEC, AGH-University of Science and Technology

Pr. Kevin OGLE, Chimie ParisTech

Dr. Polina VOLOVICH, Chimie ParisTech

Dr. Sébastien JEGOU, Arts et Métiers ParisTech

Pr. Laurent BARRALLIER, Arts et Métiers ParisTech