The Experts below are selected from a list of 537 Experts worldwide ranked by ideXlab platform
R Tewari - One of the best experts on this subject based on the ideXlab platform.
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effects of heat treatment on the extent of chromium depletion and Caustic Corrosion resistance of alloy 690
Corrosion Science, 2007Co-Authors: R S Dutta, R TewariAbstract:Abstract To quantify the extent of chromium depletion, electrochemical potentiokinetic reactivation tests were performed on solution-annealed (1393 K) and solution-annealed followed by ageing at 973 K for 4 h or 16 h samples of austenitic Alloy 690. The electrochemical studies indicated very high equilibrium chromium concentration at the chromium carbide/matrix interface for the aged samples. A new electrochemical test parameter that is the ratio of peak activation to maximum passive current density (defined by Ia/If) was considered to express the extent of chromium depletion. The alloy, in three different heat-treated conditions, revealed unstable passivity in deaerated 5% and 10% NaOH solutions at 295 K. A comparatively higher passive current density of the aged samples in deaerated Caustic environments than the annealed one could be attributed to reactivity of Cr-carbides with the Caustic. Microscopic studies indicated that the TiN inclusion/matrix interface may provide a preferred site for pit initiation in Caustic environments, which could be attributed to large degree of misfit between TiN inclusion and austenite matrix.
R S Dutta - One of the best experts on this subject based on the ideXlab platform.
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effects of heat treatment on the extent of chromium depletion and Caustic Corrosion resistance of alloy 690
Corrosion Science, 2007Co-Authors: R S Dutta, R TewariAbstract:Abstract To quantify the extent of chromium depletion, electrochemical potentiokinetic reactivation tests were performed on solution-annealed (1393 K) and solution-annealed followed by ageing at 973 K for 4 h or 16 h samples of austenitic Alloy 690. The electrochemical studies indicated very high equilibrium chromium concentration at the chromium carbide/matrix interface for the aged samples. A new electrochemical test parameter that is the ratio of peak activation to maximum passive current density (defined by Ia/If) was considered to express the extent of chromium depletion. The alloy, in three different heat-treated conditions, revealed unstable passivity in deaerated 5% and 10% NaOH solutions at 295 K. A comparatively higher passive current density of the aged samples in deaerated Caustic environments than the annealed one could be attributed to reactivity of Cr-carbides with the Caustic. Microscopic studies indicated that the TiN inclusion/matrix interface may provide a preferred site for pit initiation in Caustic environments, which could be attributed to large degree of misfit between TiN inclusion and austenite matrix.
Zhang Y - One of the best experts on this subject based on the ideXlab platform.
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effect of ni content on microstructure and high temperature Caustic Corrosion resistance of alloy cast iron
Hot Working Technology, 2013Co-Authors: Zhang YAbstract:Aimed at the problems of equipment Corrosion in Caustic soda industry,five types of Ni-Cu cast iron were developed and their Corrosion rates were tested.The results show the Corrosion resistance property can be improved clearly with the increase of Ni content,the Corrosion resistance of N4 and N5 is higher than the others.
A Navarro - One of the best experts on this subject based on the ideXlab platform.
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phosphate attack as Caustic Corrosion in high pressure boiler tubes
Materials Performance, 1999Co-Authors: M F De Romero, Orlando Perez, A NavarroAbstract:Some boiler-tube failures attributed to Caustic gouging actually have been caused by reaction of sodium phosphate species with boiler tube steel, boiler tube oxides, or both. This is referred to as phosphate Corrosion. This produces unique wastage morphologies and characteristic Corrosion products of NaFePO[sub 4]. Caustic Corrosion produces well-defined depressions or gouges, as does phosphate attack at lower sodium-to-phosphate ratios. An example is a 1,300 psi (9 MPa) and 930 F (500 C) boiler. The boiler tubes, made of ASTM A 178 GrC, failed by precipitation of the phosphates used for the chemical treatment of the boiler water, coupled with contamination of the condensate with alkaline salts. Precipitation was caused by inadequate heat flow inducing a departure from nucleate boiling (DNB), steam blanketing, and deposits.
A. U. Malik - One of the best experts on this subject based on the ideXlab platform.
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Caustic Corrosion Failure of Back Wall Riser Tube in a High-Pressure Boiler
Journal of Failure Analysis and Prevention, 2011Co-Authors: M. Mobin, A. U. MalikAbstract:This article describes the results of an investigation concerning the failure of the back wall riser tube of a high pressure boiler in a SWCC dual purpose power/water cogeneration plant. The failure occurred in one tube (facing furnace) which contained eight ruptured openings covering a length of approximately 1.8 m. The tube material was carbon steel (SA 210A1). The cause of the failure was determined by on-site visual inspection of the boiler and detailed macro and micro examinations of inner and outer scales on the tube. The in situ non-destructive testing of selected boiler riser tubes was carried out using boroscope and ultrasonic test (UT). The composition of the tube material and fire and water-side scale deposits were analyzed by energy dispersive x-ray (EDX) and inductively coupled plasma (ICP) techniques. The cause of the failure of the riser boiler tube appears to be Caustic attack. The inside brown scale that developed during service resulted in overheating, wall thinning due to Caustic Corrosion, and the associated ruptures of the tube in areas of high stress. The escaping steam eroded the outer surface of the tube resulting in heavy loss of metal around the rupture points (punch). Recommendations are given to prevent/minimize such failures.