Barry C. Syrett

Electrochemical Frequency Modulation: A New Electrochemical Technique for Online Corrosion Monitoring

Abstract Since a corrosion process is a nonlinear electrochemical phenomenon, a potential perturbation signal by one or more sine waves will generate current responses at more frequencies than the ...

Erosion-Corrosion of Copper-Nickel Alloys in Sea Water and Other Aqueous Environments—A Literature Review

Abstract The environmental and metallurgical variables affecting erosion-corrosion of copper-nickel alloys in sea water are reviewed. Other copper alloys and corrosive environments are reviewed to a limited extent, and some consideration is also given to galvanic corrosion in flowing sea water. The various laboratory test methods used for collecting erosion-corrosion data are described and discussed. It is concluded that there is an urgent need for a new approach to erosion-corrosion studies.

The accelerated corrosion of CuNi alloys in sulphide-polluted seawater: Mechanism no. 2

Abstract The corrosion behaviour of copper-nickel alloys in unpolluted and sulphide-polluted seawater has been investigated. It was demonstrated that the co-presence of sulphide and oxygen in seawater results in corrosion rates much higher than those measured when the alloy is exposed alternately to sulphide and oxygen. These high corrosion rates are comparable to the rates reported for the accelerated attack of these alloys in actual polluted estuary environments. This corrosion behavior could be modeled by considering the effect of oxygen and sulphide on the corrosion product. In aerated sulphide-polluted seawater accelerated corrosion appears to be the result of the sulphide preventing the formation of a protective oxide corrosion product layer. In the absence of a passive corrosion product, the anodic process proceeds unabated, supported by the cathodic reduction of oxygen, and extremely high corrosion rates result.

The Corrosion of Cu-Ni Alloys 706 and 715 in Flowing Sea Water. II – Effect of Dissolved Sulfide

Abstract The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in sulfide polluted flowing sea water has been studied as a function of sulfide concentration. The experimental techniques used include small amplitude cyclic voltammetry, AC impedance measurements, large amplitude cyclic voltammetry, and extensive surface examination by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction, and Auger electron spectrometry (AES). It is shown that the presence of sulfide induces a loss in passivity of the alloy surface due to the formation of cuprous sulfide as the principal corrosion product. Furthermore, accelerated corrosion of these materials in sulfide polluted sea water appears to arise from a shift in the corrosion potential to sufficiently active values that hydrogen evolution becomes a viable cathodic process.

Inhibiting mild steel corrosion from sulfate-reducing bacteria using antimicrobial-producing biofilms in Three-Mile-Island process water

Biofilms were used to produce gramicidin S (a cyclic decapeptide) to inhibit corrosion-causing, sulfate-reducing bacteria (SRB). In laboratory studies these biofilms protected mild steel 1010 continuously from corrosion in the aggressive, cooling service water of the AmerGen Three-Mile-Island (TMI) nuclear plant, which was augmented with reference SRB. The growth of both reference SRB (Gram-positive Desulfosporosinus orientis and Gram-negative Desulfovibrio vulgaris) was shown to be inhibited by supernatants of the gramicidin-S-producing bacteria as well as by purified gramicidin S. Electrochemical impedance spectroscopy and mass loss measurements showed that the protective biofilms decreased the corrosion rate of mild steel by 2- to 10-fold when challenged with the natural SRB of the TMI process water supplemented with D. orientis or D. vulgaris. The relative corrosion inhibition efficiency was 50–90% in continuous reactors, compared to a biofilm control which did not produce the antimicrobial gramicidin S. Scanning electron microscope and reactor images also revealed that SRB attack was thwarted by protective biofilms that secrete gramicidin S. A consortium of beneficial bacteria (GGPST consortium, producing gramicidin S and other antimicrobials) also protected the mild steel.

The Corrosion of Copper-Nickel Alloys 706 and 715 in Flowing Sea Water. I—Effect of Oxygen

Abstract The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in flowing seawater (1.62 m/s) has been studied as a function of oxygen concentration using the linear polarization, ac impedance, and potential step methods for measuring the polarization resistance. The high nickel alloy is found to be more corrosion resistant than the 90:10 Cu:Ni alloy under the conditions employed, provided that [O2] ≤6.60 mg/L. In oxygen saturated seawater, the superior behavior of the 70:30 Cu:Ni alloy is no longer observed. The loss in corrosion resistance of the 70:30 Cu:Ni alloy is correlated with a shift in the corrosion potential, to a value more noble than the “break-away potential” (defined here as the potential at which a sudden increase in anodic current occurs on sweeping the potential in the active to noble directions).

CORROSION OF COPPER-NICKEL ALLOYS IN SEA WATER POLLUTED WITH SULFIDE AND SULFIDE OXIDATION PRODUCTS

Abstract The corrosion rates of copper alloys 706 (90:10 Cu:Ni) and 715 (70:30 Cu:Ni) were measured, using rotating cylinder specimens in sea water that contained oxygen, sulfide, sulfur, and polysulfide, either singly or in combination. In addition a control test was performed using unpolluted deaerated sea water. Corrosion rates were monitored for over 24 hours, using linear polarization and potential step techniques. The work has shown that copper-nickel alloys can corrode quite rapidly in deaerated sea water if these normally “passive” alloys are made active by the presence of sulfide, or if sulfur is available as an oxidant.

Pitting Resistance of New and Conventional Orthopedic Implant Materials—Effect of Metallurgical Condition

Abstract The pitting resistances of four high strength, high ductility, stainless steels (TRIP steels) were compared with those of the two alloys most widely used in implants today: Type 316L stain...

Effect of Flow on Corrosion of Copper-Nickel Alloys in Aerated Sea Water and in Sulfide-Polluted Sea Water

Abstract The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in aerated sea water and deaerated sea water containing ∼ 0.2 g/m3 sulfide has been studied using a recirculating flow loop. Tubular specimens of each alloy were tested under well characterized hydrodynamic and mass transfer conditions. At sea water velocities up to 5 m/s (Reynolds numbers up to 74,000), the corrosion rates in the sulfide polluted sea water were lower than in the aerated sea water. Thus, even under comparatively adverse flow conditions, the mere presence of sulfide does not cause accelerated attack of copper-nickel alloys. These results can be compared with those of other workers who found that when both sulfide and oxygen were present in flowing sea water, the rates of corrosion of copper-nickel alloys were higher than those obtained in unpolluted aerated sea water. Under most of the experimental conditions examined, corrosion occurred fairly uniformly across the exposed surfaces of the specimens. However, in aerated sea water,...

The Validity of Electrochemical Methods for Measuring Corrosion Rates of Copper-Nickel Alloys in Sea Water

Abstract This work was stimulated by reports that electrochemical methods for measuring the polarization resistance of copper, nickel, or copper-nickel alloys in aqueous systems may lead to appreciable errors in the estimates of the corrosion rate. In the present work, the polarization resistance (Rp) of two copper-nickel alloys (90:10 Cu:Ni and 70:30 Cu:Ni) was monitored as a function of time in flowing sea water that contained 0.045, 0.85, 6.6, or 26.3 mg/dm3 dissolved oxygen. Rp values were obtained using the linear polarization, potential step, and AC impedance techniques. The total weight loss during the test period was calculated from the area under the 1/Rp versus time curve and compared with the measured weight loss. The experimental data support the validity of electrochemical methods for measuring corrosion rates of copper-nickel alloys in sea water, provided that a sufficient number of Rp measurements are made during the first 24 hours, and provided that proper consideration is given to the cap...