Download or read book ELECTROCHEMICAL STUDIES ON THE CORROSION OF CARBON STEEL IN OXALIC ACID CLEANING SOLUTIONS written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Savannah River Site (SRS) will disperse or dissolve precipitated metal oxides as part of radioactive waste tank closure operations. Previously SRS has utilized oxalic acid to accomplish this task. Since the waste tanks are constructed of carbon steel, a significant amount of corrosion may occur. Although the total amount of corrosion may be insignificant for a short contact time, a significant amount of hydrogen may be generated due to the corrosion reaction. Linear polarization resistance and anodic/cathodic polarization tests were performed to investigate the corrosion behavior during the process. The effect of process variables such as temperature, agitation, aeration, sample orientation, light as well as surface finish on the corrosion behavior were evaluated. The results of the tests provided insight into the corrosion mechanism for the iron-oxalic acid system.

Download or read book Corrosion Testing of Carbon Steel in Oxalic Acid Chemical Cleaning Solutions written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radioactive liquid waste has been stored in underground carbon steel tanks for nearly 60 years at the Savannah River Site. The site is currently in the process of removing the waste from these tanks in order to place it into vitrified, stable state for longer term storage. The last stage in the removal sequence is a chemical cleaning step that breaks up and dissolves metal oxide solids that cannot be easily pumped out of the tank. Oxalic acid has been selected for this purpose because it is an effective chelating agent for the solids and is not as corrosive as other acids. Electrochemical and immersion studies were conducted to investigate the corrosion behavior of carbon steel in simulated chemical cleaning environments. The effects of temperature, agitation, and the presence of sludge solids in the oxalic acid on the corrosion rate and the likelihood of hydrogen evolution were determined. The testing showed that the corrosion rates decreased significantly in the presence of the sludge solids. Corrosion rates increased with agitation, however, the changes were less noticeable.

Download or read book Treatment Tank Corrosion Studies for the Enhanced Chemical Cleaning Process written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radioactive waste is stored in high level waste tanks on the Savannah River Site (SRS). Savannah River Remediation (SRR) is aggressively seeking to close the non-compliant Type I and II waste tanks. The removal of sludge (i.e., metal oxide) heels from the tank is the final stage in the waste removal process. The Enhanced Chemical Cleaning (ECC) process is being developed and investigated by SRR to aid in Savannah River Site (SRS) High-Level Waste (HLW) as an option for sludge heel removal. Corrosion rate data for carbon steel exposed to the ECC treatment tank environment was obtained to evaluate the degree of corrosion that occurs. These tests were also designed to determine the effect of various environmental variables such as temperature, agitation and sludge slurry type on the corrosion behavior of carbon steel. Coupon tests were performed to estimate the corrosion rate during the ECC process, as well as determine any susceptibility to localized corrosion. Electrochemical studies were performed to develop a better understanding of the corrosion mechanism. The tests were performed in 1 wt.% and 2.5 wt.% oxalic acid with HM and PUREX sludge simulants. The following results and conclusions were made based on this testing: (1) In 1 wt.% oxalic acid with a sludge simulant, carbon steel corroded at a rate of less than 25 mpy within the temperature and agitation levels of the test. No susceptibility to localized corrosion was observed. (2) In 2.5 wt.% oxalic acid with a sludge simulant, the carbon steel corrosion rates ranged between 15 and 88 mpy. The most severe corrosion was observed at 75 C in the HM/2.5 wt.% oxalic acid simulant. Pitting and general corrosion increased with the agitation level at this condition. No pitting and lower general corrosion rates were observed with the PUREX/2.5 wt.% oxalic acid simulant. The electrochemical and coupon tests both indicated that carbon steel is more susceptible to localized corrosion in the HM/oxalic acid environment than in the PUREX/oxalic acid environment. (3) The corrosion rates for PUREX/8 wt.% oxalic acid were greater than or equal to those observed for the PUREX/2.5 wt.% oxalic acid. No localized corrosion was observed in the tests with the 8 wt.% oxalic acid. Testing with HM/8 wt.% oxalic acid simulant was not performed. Thus, a comparison with the results with 2.5 wt.% oxalic acid, where the corrosion rate was 88 mpy and localized corrosion was observed at 75 C, cannot be made. (4) The corrosion rates in 1 and 2.5 wt.% oxalic acid solutions were temperature dependent: (a) At 50 C, the corrosion rates ranged between 90 to 140 mpy over the 30 day test period. The corrosion rates were higher under stagnant conditions. (b) At 75 C, the initial corrosion rates were as high as 300 mpy during the first day of exposure. The corrosion rates increased with agitation. However, once the passive ferrous oxalate film formed, the corrosion rate decreased dramatically to less than 20 mpy over the 30 day test period. This rate was independent of agitation. (5) Electrochemical testing indicated that for oxalic acid/sludge simulant mixtures the cathodic reaction has transport controlled reaction kinetics. The literature suggests that the dissolution of the sludge produces a di-oxalatoferrate ion that is reduced at the cathodic sites. The cathodic reaction does not appear to involve hydrogen evolution. On the other hand, electrochemical tests demonstrated that the cathodic reaction for corrosion of carbon steel in pure oxalic acid involves hydrogen evolution. (6) Agitation of the oxalic acid/sludge simulant mixtures typically resulted in a higher corrosion rates for both acid concentrations. The transport of the ferrous ion away from the metal surface results in a less protective ferrous oxalate film. (7) A mercury containing species along with aluminum, silicon and iron oxides was observed on the interior of the pits formed in the HM/2.5 wt.% oxalic acid simulant at 75 C. The pitting rates in the agitated and non-agitated solution were 2 mils/day and 1 mil/day, respectively. A mechanism by which the mercury interacts with the aluminum and silicon oxides in this simulant to accelerate corrosion was proposed.

Download or read book ALTERNATIVE AND ENHANCED CHEMICAL CLEANING written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the need to close High Level Waste storage tanks, chemical cleaning methods are needed for the removal of sludge heel materials remaining at the completion of mechanical tank cleaning efforts. Oxalic acid is considered the preferred cleaning reagent for heel dissolution of iron-based sludge. However, the large quantity of chemical reagents added to the tank farm from oxalic acid based cleaning has significant downstream impacts. Optimization of the oxalic acid cleaning process can potentially reduce the downstream impacts from chemical cleaning. To optimize oxalic acid usage, a detailed understanding of the chemistry of oxalic acid based sludge dissolution is required. Additionally, other acidic systems may be required for specific waste components that have low solubility in oxalic acid, and as a means to reduce oxalic acid usage in general. Electrochemical corrosion studies were conducted with 1 wt. % oxalic acid at mineral acid concentrations above and below the optimal conditions for this oxalic acid concentration. Testing environments included pure reagents, pure iron and aluminum phases, and sludge simulants. Mineral acid concentrations greater than 0.2 M and temperatures greater than 50 C result in unacceptably high corrosion rates. Results showed that manageable corrosion rates of carbon steel can be achieved at dilute mineral acid concentrations (i.e. less than 0.2 M) and low temperatures based on the contact times involved. Therefore, it is recommended that future dissolution and corrosion testing be performed with a dilute mineral acid and a less concentrated oxalic acid (e.g., 0.5 wt.%) that still promotes optimal dissolution. This recommendation requires the processing of greater water volumes than those for the baseline process during heel dissolution, but allows for minimization of oxalic acid additions. The following conclusions can be drawn from the test results: (1) In both nitric and sulfuric acid based reagents, the low temperature and dilute concentration environment resulted in carbon steel corrosion rates that were less than 150 mpy. These rates are manageable in that chemical cleaning processes could proceed for limited time without significant wall loss. Further optimization of the Alternative Enhance Chemical Cleaning (AECC) process should focus on testing in solutions of this dilute concentration and low temperature regime. (2) In general, for the nitric acid based reagent, the aluminum oxide phase environments resulted in higher corrosion rates than the iron oxide phase environments. (3) In general, for the sulfuric acid based reagent, the iron oxide phase environments resulted in higher corrosion rates than the aluminum oxide phase environments. (4) In general, for the nitric acid based reagent, the HM sludge simulant environments resulted in higher corrosion rates than the PUREX sludge simulant environments. This result agrees with the previous observation that the aluminum oxide phases are more aggressive than the iron oxide phase environments in the nitric acid reagent. (5) Pitting was more likely to occur in the sulfuric acid based reagents than in the nitric acid based reagents. (6) Pitting occurred only in the iron based pure oxide phases and the sludge simulants. No pitting was observed in the aluminum based pure oxide phases. (7) Pitting tended to occur more frequently in tests that involved the dilute mineral acid reagent. (8) Pitting was more severe at the higher temperature for a given mineral acid concentration. (9) Pitting was more severe at a higher mineral acid concentration for a given temperature. (10) Based on the combined results of the open circuit potential and cathodic polarization testing, there was a low propensity for hydrogen evolution in solutions where sludge has been dissolved.

Download or read book Corrosion General Session written by R. G. Buchheit and published by The Electrochemical Society. This book was released on 2015-07-29 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrochemical Studies of Corrosion Inhibition of Mild Steel in Neutral Chloride Solutions written by M.A. Pech Canul and published by . This book was released on 1993 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Alternative and Enhanced Chemical Cleaning written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to develop and optimize chemical cleaning methods for the removal of sludge heels from High Level Waste tanks, solubility tests have been conducted using nonradioactive, pure metal phases. The metal phases studied included the aluminum phase gibbsite and the iron phases hematite, maghemite, goethite, lepidocrocite, magnetite, and wustite. Many of these mineral phases have been identified in radioactive, High Level Waste sludge at the Savannah River and Hanford Sites. Acids evaluated for dissolution included oxalic, nitric, and sulfuric acids and a variety of other complexing organic acids. The results of the solubility tests indicate that mixtures of oxalic acid with either nitric or sulfuric acid are the most effective cleaning solutions for the dissolution of the primary metal phases in sludge waste. Based on the results, optimized conditions for hematite dissolution in oxalic acid were selected using nitric or sulfuric acid as a supplemental proton source. Electrochemical corrosion studies were also conducted (reported separately; Wiersma, 2010) with oxalic/mineral acid mixtures to evaluate the effects of these solutions on waste tank integrity. The following specific conclusions can be drawn from the test results: (1) Oxalic acid was shown to be superior to all of the other organic acids evaluated in promoting the dissolution of the primary sludge phases. (2) All iron phases showed similar solubility trends in oxalic acid versus pH, with hematite exhibiting the lowest solubility and the slowest dissolution. (3) Greater than 90% hematite dissolution occurred in oxalic/nitric acid mixtures within one week for two hematite sources and within three weeks for a third hematite sample with a larger average particle size. This dissolution rate appears acceptable for waste tank cleaning applications. (4) Stoichiometric dissolution of iron phases in oxalic acid (based on the oxalate concentration) and the formation of the preferred 1:1 Fe to oxalate complex is possible with the addition of a supplemental hydrogen ion source (HNO3 or H2SO4) and pH control. (5) Sulfuric acid is nearly twice as effective as nitric acid (on a molar basis) at promoting hematite dissolution in oxalic acid solutions, most likely due to the fact that it is diprotic. (6) The greater the oxalic acid concentration, the greater the demand for supplemental H to promote optimal dissolution. Minimum mineral acid concentrations required for optimal oxalic acid utilization based on hematite solubility tests are provided. (7) Corrosion studies conducted (reported elsewhere) with 1 wt.% oxalic acid revealed that carbon steel corrosion rates are manageable at lower mineral acid concentrations (0.1 M HNO3 and 0.05 M H2SO4) and lower temperatures (45 C). (8) Proposed conditions for waste tank heel dissolution based on the solubility and corrosion test results are 0.5 wt.% oxalic acid and 0.18 M HNO3 or 0.09 M H2SO4 at 50 C. (9) The OLI Thermodynamic Model appears to over-predict the solubility of the iron phases studied in oxalic acid and oxalic/nitric acid mixtures. The predictions show better agreement with experimental results at higher pH and in sulfuric/oxalic acid mixtures. (10) Oxalic, nitric, and sulfuric acids are effective at quickly dissolving gibbsite (e"6% dissolution in 2 weeks), with oxalic/sulfuric acid mixtures being particularly effective. (11) Limited dissolution tests conducted with carbon steel coupons revealed that the presence of metallic iron can, in some cases, result in dramatically different results. Additional studies in this area are recommended. Based on the current results, the optimal approach for the removal of sludge heels for HLW tanks would include the following steps: (1) removal of the maximum possible amount of heel materials by mechanical means; (2) neutralization and acidification of the heel using dilute mineral acid (This step should promote significant dissolution of certain metal hydroxides and salts, including gibbsite.); and (3) dissolution of the residual heel material at 50 C using an acid mixture containing 0.5 wt.% oxalic acid and 0.18 M nitric acid (This step should dissolve the iron phases.).

Download or read book Organic Compounds as Corrosion Inhibitor of Carbon Steel in Acid Media written by Ali Anejjar and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lectures on Electrochemical Corrosion written by Marcel Pourbaix and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Workers in the field of corrosion and their students are most fortunate that a happy set of circumstances brought Dr. Marcel Pourbaix into their field in 1949. First, he was invited, while in the USA, to demonstrate at a two week visit to the National Bureau of Standards the usefulness of his electro chemical concepts to the study of corrosion. Secondly, also around the same time, Prof. H. H. Uhlig made a speech before the United Nations which pointed out the tremendous economic consequences of corrosion. Because of these circumstances, Dr. Pourbaix has reminisced, he chose to devote most of his efforts to corrosion rather than to electrolysis, batteries, geology, or any of the other fields where, one might add, they were equally valuable. This decision resulted in his establishing CEBELCOR (Centre BeIge d'Etude de la Corrosion) and in his development of a course at the Free University of Brussels entitled "Lectures on Electrochemical Corrosion." This book is the collection of these lectures translated into English.

Download or read book Electrochemical Techniques Applied to the Study of Mild Steel Corrosion in 1 0 1 and 0 001 Na2SO4 Solutions written by J. Mendoza-Flores and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book SAVANNAH RIVER SITE TANK CLEANING written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. Both the 1-wt% and the 8-wt% testing demonstrated that if the sludge was removed from the testing, there would be a significant increase in the CR. Specifically, the CR for an agitated 1-wt% pure oxalic acid solution at 45 or 75 C was about 4 to 10 times greater than those for a 1-wt% solution with sludge. For 8-wt% at 50 C, the effect was even larger. The lower CRs suggest that the cathodic reactions were altered by the sludge. For both the 1-wt% and 8-wt% solution, increasing the temperature did not result in an increased CR. Although the CR for a 1-wt% acid with sludge was considered to be non-temperature dependent, a stagnant solution with sludge resulted in a CR that was greater at 45 C than at 75 C, suggesting that the oxalate film formed at a higher temperature was better in mitigating corrosion. For both a 1 and an 8-wt% solution, agitation typically resulted in a higher CR. Overall, the testing showed that the general CR to the SRS carbon steel tanks from 1-wt% oxalic acid solution will remain bounded by those from an 8-wt% oxalic acid solution.

Download or read book Electrochemical Studies of Corrosion Inhibitors written by Merlin D. Danford and published by . This book was released on 1990 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Electrochemical Study of the Corrosion Behaviour of Metallic Coatings on Carbon Steel Strips written by Abdo Ahmed Maqbul and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrochemical Studies of Some Corrosion Inhibitors on Mild Steel written by Dusit Ungthararuk and published by . This book was released on 2000 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrochemical Studies of Corrosion Inhibition of Mild Steel written by Awad Sadek Mogoda and published by LAP Lambert Academic Publishing. This book was released on 2014-03 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: The corrosion inhibition of steel in 1.0 M sulfuric acid by some triazole derivatives namely, 4-amino-1,2,4-triazole-3-thiol (ATT), 4-amino-5-methyl-1,2,4-triazole-3-thiol (AMTT) and 4-amino-5-ethyl-1,2,4-triazole-3-thiol (AETT) has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Scanning electron microscopy (SEM). The results revealed that the inhibition efficiency increases as the inhibitor concentration increases and follows the order (ATT

Download or read book Electrochemical corrosion studies on a selected carbon steel for application in nuclear waste disposal containers written by Anne-Marie Farvaque-Béra and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metals Abstracts written by and published by . This book was released on 1996 with total page 1628 pages. Available in PDF, EPUB and Kindle. Book excerpt: