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A combination of thermodynamic analyses and potentiodynamic polarization tests have been used to study the anodic behavior of Cu in strong H2S04 solutions in the concentration range 1-10 M. The studies were supplemented by chemical analyses of surface films. It was found that concentration-dependent changes in the activity of water played a major role in determining the anodic behavior and relative stability of corrosion product films. The anodic Tafel slope decreased from -41 to -31 mV with increasing acid concentration. The onset of limiting current and active-passive behaviors at higher potentials was determined by the formation of films of hydrated copper sulfate, CuSO4xH2O, and not by formation of oxides. Limiting current behavior was observed in 1 M solutions, where the degree of hydration was x =5. Welldeveloped passivity occurred in 10 M solutions where x = 1. The results are relevant to industrial electrorefining operations for Cu and indicate that chloride contamination, if present in sufficient amounts, could cause the premature onset of limiting current behavior (anode "passivity") during refining.

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An experimental investigation was carried out to measure transgranular stress corrosion crack growth rates (CGR) in precracked X-60 steel specimens exposed to neutral (pH 7) dilute simulated ground water (designated NS4) while being cyclically loaded in cantilever bending. Testing was carried out over short-term (generally < 40 days) and long-term periods (~ 1 y). Loading and environmental conditions in the long-term tests were similar to those for buried natural gas pipelines, with the R ratio (minimum/maximum load) varying from 0.82 to 0.98 and frequencies ranging from 1 to 400 cycles/day. Cyclic loading conditions for specimens in the short-term tests were more severe, with R ratios ranging from 0.5 to 0.9 and frequencies from 40 cycles/day to 5,000 cycles/day. Post-mortem metallographic examination by optical (OM) and scanning electron microscopy (SEM) was used to evaluate crack growth. Average CGR from 4.50 x 10 -8 mm/cycle to 1.25 x 10 -4 mm/cycle (equivalent to 1.4 x 10 -9 mm/s to 7 x 10 -7 mm/s) were measured, depending upon applied load range. For the more severe loading conditions in the short-term tests, the observed growth was attributed to corrosion fatigue. Under the less severe loading conditions of a high R ratio and low frequency, growth was attributed to transgranular stress corrosion cracking.

This paper wss selected for presentation by an SPE Pmgrsm Commkfollowing ra'view of information mntsined in an abstmct subm"tied by the author(s), Contents of the papar, as pmsentsd, ham not been reviewed by the society of Petroleum Engin8er8 and am subject to m~on by the author(s). The material, as pmsantd, d-nd necessarily reflect any pm~on d the Smiety~Petroleum Enginwm, its officers, or members. Papers presented at SPE meetings ara subject to publics.tion review by Editorial Committees of the Mety of Ptileum Engineers. Elactmnic reproduction, distribution, or storage of any part of this papar for commercial pu~s without the written wnsent of the Society of Petroleum Engineers is pmhib~. permission to reproduce in print is restricted to an abstict of na more thanw ords, illusbstions may rmt h copied. The abstrmt must mntain rnnspicuous ackndedgment &where and by Mom the papr wss pressn~. Writa Librarian, SPE, PO. Sm S33S3r3, Richardson, TX 7-3S3e, U.S.A., f= 01 -972-9S2-942S. AbstractSince Saudi Aramco's seawater injection system was commissioned in 1978, it has undergone a series of expansions and modifications. The~stem is unique, not only in its size (7 million barrels per day capacity), but also in its complicated piping network. While the original piping system was completely made of bare carbon steel, the new system is made of pipe which is internally coated with fusion

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