Electrochemical determination of corrosion protection and phase composition of nitride layers on steels

Electrochemical method providing the possibility to check the penetrating porosity, corrosion resistance and phase composition of nitrided surface has been developed and applied for high-speed SW18 steel nitrided from plasma excited H2 +N2 gas mixture and for structural 10A and 45A steels nitrided from NH3 gas dissociated at different parameters. By selection the appropriate electrolytes, the phase composition of nitrided layer in SW18 steel, and the corrosion resistance of e or γ' compact nitride layer on 10A and 45A steels have been evaluated and confirmed by material science and corrosion tests. Electrochemical methods may be applied to control the quality of obtained nitrided layer, and to correct or modify the program of technological process. Electrochemical method provided the possibility to check the penetrating porosity, corrosion resistance and phase composition of nitrided surface By selection the appropriate electrolytes, the phase composition and the corrosion resistance of nitride layers formed on SW18, 10A and 45A steels were established in accordance with the material investigation and corrosion tests data

Some disturbing trends in the levels of habitual physical activity in Hong Kong primary school children: preliminary findings

Hydrogen embrittlement has caused many service failures in linepipe steel. Service conditions present several avenues by which hydrogen can adversely affect the mechanical properties of such steel. Fesseler [1] reported that local mechanical damage can arise from handling and laying of pipe and that some cathodic protection schemes can in fact inject dangerous amounts of hydrogen into a steel. There can be synergism between these two aspects which can give extremely high hydrogen charging conditions resulting in failure [2]. Metallurgists in the oil and gas industries refer to this type of failure as hydrogen stress cracking (HSC). Future synthetic natural gas from coal gasification may contain as much as 50% H2 which will be very deleterious to linepipe properties. Sulfides present in natural gas, hydrogen sulfide or carbon disulfide, tend to inhibit the recombination of 2HADS → H2and therefore favor atomic hydrogen absorption into a steel [3]. Welding of linepipe is a potential source of nearly every known hydrogen problem depending on the circumstances of the technique [4]. Thus it is apparent that NDE techniques adaptable to field use will be important to the maintenance of thousands of miles of existing and future pipelines. The particular use of positron annihilation to be described could be one such technique