Stability of passive film on advanced Ni-base alloy
- Reference number
- ID19-0032
- Project leader
- Pan, Jinshan
- Start and end dates
- 200101-251231
- Amount granted
- 2 500 000 SEK
- Administrative organization
- KTH - Royal Institute of Technology
- Research area
- Materials Science and Technology
Summary
Ni-base alloys are increasingly used in a wide range of industrial applications due to their high performance, high durability and recyclability. They form spontaneously a thin passive film on the surface, which prevents rapid corrosion in corrosive environments. However, sometimes, passive film breakdown and corrosion initiation may occur, leading to economic, environmental and even human disasters. Advanced Ni-base alloys possess excellent mechanical properties and corrosion resistance, but detailed knowledge is lacking about their passive film and breakdown. In this industrial PhD project jointly proposed by Div. of Surface and Corrosion Science at KTH Royal Institute of Technology and Sandvik Materials Technology, the main objectives are to gain fundamental understanding of the dynamic nature and stability of the passive film of Ni-base alloys with high contents of Cr and Mo, and the passivity breakdown and corrosion initiation in typical corrosive environments. Combined electrochemical and in-situ surface analyses will be performed to study the chemical and structural changes of the passive film during the breakdown, using state-of-the-art local probing methods and world-class synchrotron techniques. The expected results include detailed knowledge of the influence of Ni, Fe, Cr and Mo in the alloy on the stability of the passive film, and the effect of electrochemical potential, pH, temperature and chloride concentration of the solution on the passive film breakdown.
Popular science description
Metallic materials are one of the corner stones of our society. Alloys such as stainless steels and nickel alloys play an important role in the sustainable development. These alloys exhibit stability in service due to spontaneous formation of a thin passive film on the surface, which prevents rapid corrosion during the service in corrosive environments. However, sometimes, passive film breakdown and corrosion may occur, leading to economic, environmental and even human disasters. Advanced nickel alloys contain several alloying elements and have excellent mechanical properties and corrosion resistance. They are increasingly used in a wide range of industrial applications, especially when stainless steels do not fulfill the requirements, e.g., in nuclear energy, chemical/petrochemical industry, oil and gas industry, etc. The passivity of stainless steels has been studied extensively and there is knowledge about thermodynamics, kinetics and electrochemical characteristics of the passivity. However, little is known about the passive film and breakdown of nickel alloys, in particular the protective properties of the passive film in the solution and its changes occurring during the breakdown. This prevents scientific explanation of the observations regarding the stability and corrosion of nickel alloys. This industrial PhD project is a collaborative effort between Div. of Surface and Corrosion Science at KTH Royal Institute of Technology and Sandvik Materials Technology, to improve the knowledge of the passivity and breakdown of advanced nickel alloys. The main objectives are to gain fundamental understanding of the dynamic nature of the passive film of nickel alloys with high chromium and molybdenum contents, and the passivity breakdown in typical corrosive environments. By using state-of-the-art local probing methods and world-class synchrotron techniques, we will perform combined electrochemical and surface analyses in real time to study the chemical and structural changes of the passive film during the breakdown. The results will provide detailed knowledge of the influence of nickel, iron, chromium and molybdenum in the alloy on the stability of the passive film, and the effect of electrochemical potential, pH, temperature and chloride concentration of the solution on the passive film breakdown. The new knowledge will benefit the design and improvement of advanced nickel alloys, and development of new corrosion test methods for the nickel alloys.