Corrosion Science and Technology Group
Materials Science & Technology Division
Oak Ridge National Laboratory
Post Office Box 2008, Mail Stop 6156
One Bethel Valley Road
Oak Ridge, Tennessee 37831-6156
865-574-45138
pawelsj@ornl.gov
Current Projects:
Investigation of corrosion and compatibility issues associated with the target station of the Spallation Neutron Source. Primary thrust of the project is focussed on thermal gradient mass transfer and liquid metal embrittlement effects associated with containment of mercury (the target material). Experimental effort includes examination of stainless steels and selected nickel-base alloys in thermal convection loops containing mercury as well as fatigue and tensile properties of candidate containment materials in mercury. Water-side cooling corrosion issues are also a portion of this effort.
Technical Project Manager for the UF6 Cylinder Project. The Department of Energy owns 50,000+ large mild steel cylinders containing the tails of the uranium enrichment process (depleted uranium hexafluoride) which have been stored outdoors (many for as long as 40+ years) on large storage yards. A major component of this task is statistically-based wall thickness measurements and modeling to assess cylinder inventory condition and container corrosion rate. In addition, the task includes selection, implementation, and performance monitoring of corrosion mitigation techniques such as blasting/coating and storage yard improvements, and structural/mechanical assessments to support cylinder handling protocols and return-to-service calculations for these ASME pressure vessel containers. The task also includes function as the project liaison to the Defense Nuclear Facility Safety Board.
Material characterization for the pulp and paper industry. This task includes metallurgical assessments of failed components from black liquor recovery boilers and pulp digesters to determine failure mechanisms. The goal of the effort is to collect sufficient information that alternative materials and processes can be selected to improve safety and performance.
Chemical process control, failure analysis, and material selection - aqueous corrosion studies in support of material selection for chemical processes at ORNL. Experimental techniques include coupon immersion studies, electrochemical polarization, electrochemical noise, and specialized development of prototypic test stands to examine process variables.
Recent Research and Development Efforts:
Lithium hydride corrosion of steels, stainless steels, and high alloys materials was examined as a function of temperature and cover gas composition variables. An experimental test apparatus and salt handling procedure was developed to mimic the process of interest. The activation energy for the corrosion process was determined, corrosion rates under various conditions documented, and mechanisms for attack in various metals elucidated.
Corrosion/oxidation studies in support of the Advanced Neutron Source core design were performed. A complex experimental facility to simulate appropriate core conditions (very high flow rates, very high heat transfer, and precise cooling water temperature and chemistry control) was developed. Results of oxide growth on aluminum core cladding materials as a function of water variables and thermal-hydraulic conditions were used to generate an improved correlation for prediction of scale thickness and acceptable operating conditions to minimize aluminum corrosion. Corrosion of aluminum in spent fuel storage basins has also been examined.
Immersion studies of coating systems to select materials for immersion duty in waste process tanks were performed. Experiments included panel exposures of 20+ materials for up to 15 months in a range of process solutions from pH 1-13 with and without cathodic protection superimposed. The task included an effort to devise a scheme to rate the relative performance of each system using degree of discoloration, swelling, toughness/flexibility retention, chipping and undercut at an "X" scratch, degree of blistering, and retention of pull-off adhesion strength. Specifications for application of the superior systems to tank interiors were developed and inspection procedures implemented.
Stress corrosion cracking studies for ORNL and area industries have been undertaken. Recent examples include examination of cracking tendency of:
- white gold alloys in ferric chloride solutions;
- high-nickel alloys in HF process environments;
- brass containers in ambient atmosphere and nitrogen compound environments;
- recovery boiler floor tubes taken from service;
- low-level radioactive waste evaporator tubing;
- caustic storage tank materials of construction;
- high alloy materials in acid mixtures representing a waste process facility.
Education:
- Ph.D. in Metallurgical Engineering (University of Tennessee, 1987)
Dissertation: The Role of Nitrogen in the Localized Corrosion Resistance of Cast Duplex Stainless SteelsProfessional Affiliations:
- Member of ASM International (1978-present)
- Member of NACE (1980-present)
- Member of TAPPI (1999-present)
Open Literature Publications:
- S. J. Pawel,"Observations of Containment Corrosion in the Vapor over Lithium Hydride in the Temperature Range 600-800¡C," Journal of Nuclear Materials, Vol. 218, p.302 (1995).
- S. J. Pawel, J. R. Keiser, and H. F. Longmire, "Investigation of the Liquid Low Level Waste Evaporator Steam Coil Failure and Supporting Laboratory Studies," ORNL/TM-12974, May 1995.
- S. J. Pawel, D. K. Felde, and R. E. Pawel, "Influence of Coolant pH on Corrosion of 6061 Aluminum Under Reactor Heat Transfer Conditions," ORNL/TM-13083, October 1995.
- S. J. Pawel, R. J. Lopez, and E. Ondak, "Chemical and Environmental Influences on Copper/Copper Sulfate Reference Electrode Half Cell Potential," Materials Performance, Vol.37, No. 5, p.24 (1998).
- S. J. Pawel, et. al., "Screening Test Results of Fatigue Properties of Type 316LN Stainless Steel in Mercury," ORNL/TM-13759, March 1999.
- S. J. Pawel, J. R. DiStefano, and E. T. Manneschmidt, "Corrosion of Type 316L Stainless Steel in a Mercury Thermal Convection Loop," ORNL/TM-13754, April 1999.