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Galvanic Corrosion
Galvanic corrosion is an electrochemical reaction in which one metal corrodes preferentially when in electrical contact with a different type of metal and both metals are immersed in an electrolyte. When two or more different kinds of metals come into contact in the presence of an electrolyte a galvanic couple is set up as different metals have different electrode potentials. The electrolyte provides a mode for ion migration whereby metallic ions can move from the anode to the cathode. This leads to the anodic metal corroding more quickly than it otherwise would; the corrosion of the cathodic metal is reduced. This section contains reports related to galvanic corrosion.
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Electrochemical Testing of Drill Collar Alloys
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Galvanic corrosion measurements were conducted (ASTM G-71) between drill collar and shock sleeve alloys and cyclic potentiodynamic polarization scans (ASTM G-61) on drill collar alloys for the determination of susceptibility to localized corrosion in simulated drilling fluid. The drill collar alloys selected for the program were (1) AG-17, (2) P550,
(3) P530, (4) P530HS, (5) NMS 100, (6) SMF 166, (7) 15-15LC Modified, and (8) Staballoy 734, and the shock sleeve alloys chosen were Spinodal (CDA ...
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This report is available for download to corporate users only at this time and will be soon made available for individual purchase.
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Galvanic Corrosion of Nitrided Materials
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Coupons of nitrided and non-nitrided 9Cr and 13Cr were exposed to a simulated downhole environment (250 F, 200 psia CO2, 1 psia H2; aqueous phase of 5 percent NaCl). Coupons were fixtured in a static autoclave such that galvanic effects between sets of coupons could be determined. One group of 16 coupons was exposed to the vapor phase of the autoclave and 1 group of sixteen coupons was exposed to the liquid phase.
Vapor phase corrosion was found to be minimal from the standpoint of weight loss....
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This report is available for download to corporate users only at this time and will be soon made available for individual purchase.
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Galvanic Corrosion of Drill Collar Alloys
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Galvanic corrosion occurs when two dissimilar materials in electrical contact are simultaneously exposed to a corrosive fluid. In general, the more active alloy of the couple corrodes preferentially while the less active (more noble) material is cathodically protected. The rate of galvanic corrosion is a function of several variables including area ratios, corrosivity of the medium, temperature, fluid velocity, nature of the materials, etc.
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This report is available for download to corporate users only at this time and will be soon made available for individual purchase.
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