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INTRODUCTION ABSTRACT Corrosion rate studies were conducted in the laboratory on high total dissolved solids (TDS), zero liquid discharge (ZLD) cooling water. The cooling water had been treated with silica corrosion inhibitor chemistry in the field operating system. Corrosion rates were measured using real time coupled multi-electrode array sensor technology. The study evaluated both general and localized (pitting) corrosion rates for carbon steel (CS), copper, aluminum, zinc and stainless metals at temperatures ranging from 77 to 190° F (25 to 88° C). . The study confirmed that the silica chemistry provided exceptional corrosion inhibition with very low corrosion rates (i.e.,<0.3 mpy [0.0076 mm/yr] on1008 CS) for mild carbon steel at high TDS and temperature extremes, as well as exceptionally low corrosion rates on other metals evaluated. The laboratory study corroborated field corrosion results, and established this procedure as a potentially efficient means of predicting corrosion inhibitor performance with various metals and water temperatures in field systems with given system water chemistry and inhibitor residuals. . The "Green Chemistry" corrosion inhibitor evaluated was silica (SiO2) which is controlled at concentrations between 200 mg/L and saturation, typically greater than 300 mg/L as soluble SiO2), provided through evaporative concentration and conversion of natural silica in the source water. Most operators are reluctant to try new technologies in their full scale operations fearing failure and disruptions of production. This fear can be overcome if sufficient confidence can be gained from bench or pilot scale investigations. In pursuing the development of silica chemistry as described in this paper, the authors have demonstrated that by using the corrosion monitoring techniques described, the performance at the pilot level matches the performance in full operations. Confidence in transferring pilot data to full operations Silica chemistry can prevent corrosion in high TDS waters and Silica chemistry qualifies as "green" inhibitor chemistry As more oil and gas plants move to zero liquid discharge (ZLD), they are choosing to use demineralized water as cooling water make-up in order to reduce the amount of blow down to be sent to the evaporator/crystallizer systems. Chemical treatments of such systems are challenging with traditional inhibitor chemistry and therefore the opportunity to consider this proposed silica chemistry becomes very relevant for the industry. Three main objectives have therefore been met. Silica Chemistry Silica has been one of the major scale and fouling problems in many processes that use water. Silica is difficult to deal with because it can assume many low solubility chemical forms, depending on the water chemistry and metal surface temperature conditions. Below about pH 9.0, silica (monomer) has limited solubility (125-180 mg/L as SiO2, at 77° F) and tends to precipitate as these concentrations are exceeded with the insoluble salts of polyvalent metal ions (hardness) in source waters. In industrial applications, most scale and corrosion control methods used in evaporative cooling water systems typically rely on the addition of a scale and corrosion inhibitors in combination with controlled blow down wastage of system water to prevent scale and corrosion problems.
- Materials > Chemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Lifecycle > Discharge (0.81)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Corrosion Behavior Of Alloy 22 In Concentrated Nitrate And Chloride Salt Environments At Elevated Temperatures
Yang, Lietai (Southwest Research Institute) | Dunn, Darrell (Southwest Research Institute) | Cragnolino, Gustavo (Center for Nuclear Waste Regulatory Analyses) | He, Xihua (Center for Nuclear Waste Regulatory Analyses) | Pan, Yi-Ming (Center for Nuclear Waste Regulatory Analyses) | Csontos, Aladar (U.S. Nuclear Regulatory Commission) | Ahn, Tae (U.S. Nuclear Regulatory Commission)
ABSTRACT The possible waste package design at the potential repository at Yucca Mountain, Nevada, may consist of an outer container made of Alloy 22. Under the repository conditions, hygroscopic salts may deposit on the waste package surfaces and sorb moisture from the atmosphere when the relative humidity is near or above their deliquescence relative humidity, causing aqueous corrosion of the waste package. The corrosion rates of Alloy 22 in the liquid and vapor phases in a system containing an equimolar NaCl-NaNO3-KNO3 mixture were measured at temperatures ranging from 150 to 180 °C [302 to 356 °F]. Also, polarization curves and open-circuit potentials were obtained in the liquid phase. To simulate the potential Yucca Mountain emplacement drift condition, the experiments were conducted under ambient pressure, and the test system was not deaerated. No significant localized corrosion was observed, and general corrosion was found to be the primary mode of attack. The general corrosion rates measured in the liquid phase from mostly thermally-aged specimens in preliminary short-term tests were from 1 to 10 µm/yr [0.04 to 0.4 mil/yr]-significantly higher than the rates obtained under autoclave conditions and reported in the literature. Further experiments are underway to verify these preliminary results. INTRODUCTION Alloy 22 is a nickel-chromium-molybdenum alloy (Ni-22Cr-13Mo-4Fe-3W) which is highly corrosion resistant in oxidizing environments. Because of its high resistance to corrosion, Alloy 22 is being considered as the outer container material in the possible waste package design at the potential high-level waste repository at Yucca Mountain, Nevada. The waste package may assist in preventing or delaying release of radioactive material to the public before and after permanent closure. Under a nominal-case scenario, corrosion is considered to be the primary degradation process limiting the lifetime of the waste package. Loss of containment will allow radionuclides to be released to the environment immediately surrounding the waste packages. During the preclosure period, expected to last for 50 to 300 years, the drifts of the potential repository will be ventilated for at least part of the time. Atmospheric aerosols and dusts may be introduced into the drift by the ventilation and lead to accumulation of hygroscopic salts on the waste package surfaces. The hygroscopic salts on the waste package surfaces could sorb moisture from the atmosphere and form brine solutions on the waste packages when the relative humidity is near or above their deliquescence relative humidity, promoting the corrosion of waste package materials. The soluble component of aerosol and dust in a given geographic area are directly related to the soluble constituents in rainfall in the area. According to the National Atmospheric Deposition Program, sodium, potassium, nitrates, and chlorides are among the principal soluble cation and anion constituents in the wet precipitation samples collected at Death Valley, California, which is close to Yucca Mountain. Because of the hygroscopic nature of the NaCl-NaNO3-KNO3 salt solutions, their boiling points are extremely high and may be higher than 220 °C [428 °F] at ambient pressure.
- Water & Waste Management (1.00)
- Materials > Metals & Mining (1.00)
- Materials > Chemicals (1.00)
- (2 more...)