Corrosion Product Analysis

The measurement of fluid corrosivity using probes and coupons should be supplemented by the chemical analysis of any corrosion products or deposits that are found, either on the probes and coupons or on the internals of the process equipment during plant inspections. 

The following techniques may be used to examine corrosion products. 

The collection, handling, and storage of corrosion products should he in such a manner as to avoid contamination and/or degradation of the sample. Detailed examination should he carried out as soon as possible after removal from the system. 

Recommended procedures for the collection and identification of corrosion products are given in NACE Standard RP0173. 

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CORROSION RATES FROM CORROSION PRODUCT ANALYSIS... 

S. N. Smith 2003. Corrosion product analysis in oU and gas pipelines. Materials Performance 42 (8),... 

Other Useful Information Obtained by Probes Both EIS and electrochemical noise probes can be used to determine information about the reactions that affect corrosion. Equivalent circuit analysis, when properly applied by an experienced engineer, can often give insight into the specifics of the corrosion reactions. Information such as corrosion product layer buildup, or inhibitor effectiveness, or coating breakdown can be obtained directly from analysis of the data from EIS or indirectly from electrochemical noise data. In most cases, this is merely making use of methodology developed in the corrosion laboratory. 

Oxygen corrosion involves many accelerating factors such as the concentration of aggressive anions beneath deposits, intermittent operation, and variable water chemistry. How each factor contributes to attack is often difficult to assess by visual inspection alone. Chemical analysis of corrosion products and deposits is often beneficial, as is more detailed microscopic examination of corrosion products and wasted regions. 

X-ray analysis of corrosion products and deposits removed from internal surfaces showed 68% iron, 12% phosphorus, 8% silicon, 3% sulfur, and 2% each of zinc, sodium, chromium, and calcium other materials made up the remainder of deposits and corrosion products. 

Chemical analysis showed that each organism contained up to 50% silica by weight. Each was coated with iron oxides, silt, and other deposits and corrosion products. In places, large deposit accumulations were clearly correlated with large numbers of organisms. 

The above analysis indicates that the high concentrations of sulfur-containing deposits and corrosion products were caused by the influence of large organisms. Bacterial contributions to corrosion and associated fouling were minimal. 

Removal of deposits and corrosion products from internal surfaces revealed irregular metal loss. Additionally, surfaces in wasted areas showed patches of elemental copper (later confirmed by energy-dispersive spectroscopy) (Fig. 13.12). These denickelified areas were confined to regions showing metal loss. Microscopic analysis confirmed that dealloying, not just redeposition of copper onto the cupronickel from the acid bath used during deposit removal, had occurred. 

An irregular trough of metal loss is apparent along the circumference of the ring (Fig. 16.4). Metal loss is severe near the nozzle holes (Fig. 16.5). The corroded zone is covered with light and dark corrosion products and deposits. Analysis of these revealed substantial quantities of copper and zinc. Microscopic examinations revealed exfoliation of the aluminum ring in corroded regions. 

This is primarily engaged in analysis of boiler water treatment matters and involves on-site studies of various problems and the chemical examination of corrosion products, boiler scales, etc. It can also carry out certain types of metallurgical, fuel and inorganic analysis. Normal wet methods of analysis coupled with a visible ultraviolet and atomic absorption spectrophotometer are used for a wide range of analytical applications. Equipment in use by the engineering insurers providing these services can include an ion chromatograph, spectrometer equipment, atomic... 

In cases such as this, the possible contamination of the solution by corrosion products may be estimated from the loss in mass of the test specimen. This, however, does not make any distinction between soluble and insoluble corrosion products, which may have different effects and which can be studied best by chemical analysis of the test solution and the materials filtered from it. Similarly, chemical analysis may be required to detect any other changes in the composition of the test solution that may be of interest. 

The method can successfully be used in analyses of impurities in metals and alloys, for estimation of minor elements in monomolecular films of oxide layers of Fe-Cr-Ni alloys, for detection of metal impurities in environmental pollution, for studying the depression of high-grade semiconducting materials and for analysis of the corrosion products of contact junction diodes used in microelectronic circuits. Much sophistication is desirable on the instrumental side so as to incorporate an automatic recording device to make an FR polarograph suitable for wider applications and common use. 

In the museum context, nondestructive (or quasi-nondestructive) techniques such as X-ray fluorescence (XRF) (Chapter 5) are often preferred for the analysis of inorganic objects, although microanalysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) (Chapter 9) is growing in importance, since the ablation craters are virtually invisible to the naked eye. Raman and infrared spectroscopy (Chapter 4) are now being used for structural information and the identification of corrosion products to complement X-ray diffraction (Section 5.4). 

The liquid effluent, which consists of water from the evaporator/crystallizer used to produce the solid filter cake produced by the brine-recovery operation, should not pose a significant hazard to human health or to the environment. While the evaporator/crystallizer system has not been tested yet, the composition of the water and solid filter cake can be readily determined from an analysis of the SCWO liquid effluent. As shown in Table 5-10, the liquid effluent is essentially free of organics. The source of the chromium and nickel that were found in some of the effluents is generally believed to be corrosion products from the SCWO reactor components. These elevated levels of metals indicate that the solid filter cake will need to be treated (e.g., by stabilization) prior to disposal in a hazardous waste landfill. 7... 

On the other hand, the P—E bond is rather labile toward hydrolysis by even trace amounts of moisture in nonaqueous solvents, producing a series of corrosive products (Scheme 5). Thermal gravimetric analysis (TGA) reveals that, in a dry state, LiPFe loses 50% of its weight at >200 °C but that, in nonaqueous solutions, the deterioration occurs at substantially lower temperatures, for example, as low as 70 X. 

Information about the corrosion of boiler piles comes from analysis of scale samples and also from laboratory experiments. Smith and McEaney (1979) used XRD and SEM to follow the initial stages in the development of scale on gray, cast iron in water at 50 °C. At first, the corrosion product was a mixture of magnetite and green rust. Whether lepidocrocite formed depended on the level of oxygen in the system. 

Tahiti 3. Radiochemical analysis oj corrosion products Jrom spent fuel ajtvr 1.5 v of immersion in wilier... 

Two characteristic times can be identified in the analysis of accidents. For the most corrosive products, penetration starts after the first 10 s. This penetration is nearly total after 1 min. The symptoms and their occurrence depend on the seriousness and reversibility of the corrosive or irritating product and its concentration. 

The heavy corrosion layer on tablet P6 was analyzed using X-ray diffraction (XRD) in order to identify the products that had formed. The corrosion on P6 contained all the different types of corrosion observed on other tablets to date. Corrosion products were considered a possible reason fin- variation in the ICP-MS results, but not the TIMS results. XRD analysis bombards the sample with X-rays of one wavelength and determines the distance between atoms and atomic units in the sample. Diffraction of the X-rays occurs at different angles and intensities depending on the minerals in the sample. The diffractograms are compared to known standards to determine what minerals are present in the sample. 

Data Analysis. Data analysis is, of course, directly related to data acquisition. However, not all good data is or can be completely analyzed. For example, McIntyre (J5) has observed that "a broad base in chemical shift data has been slow in developing" for XPS data. Until such a data base existed, it was difficult for both expert and non-expert to interpret spectra from corrosion products, particularly on complex alloys. The Handbook of X-Ray Photoelectron Spectroscopy (27) and collections of Auger parameter data (32 ) are examples of data compilations very useful to a researcher trying to interpret measurements of corrosion products. 

Radioactivity transport in reactor coolant circuits involves both surface corrosion and deposition. Several XPS studies(8,9) of reactor boiler alloys have been reported which show the very strong effect of coolant chemistry on the films deposited. The chemistry of corrosion products precipitated on ZrO and Al O surfaces has been studied using XPS.ly More recently, chemical decontamination of radioactive boiler circuits has been assisted by XPS analysis of the surface-active decontaminating agent.(1 ) Surface oxidation in gas-cooled reactor circuits has also been investigated. AES has been used to follow the CC>2 oxidation of a chromium steel(H) and some pure metals. (12)... 

Where contaminants may cause a reaction, careful design is required to minimize the risk of contamination. Corrosion products are a common contaminant selecting appropriate materials of construction is important in these cases. Where the contaminant is present in other parts of the process, routine analysis of feedstreams is important. If water can cause a reaction both design and operational measures may be required. Water may enter the process by many routes (utility connections, faulty tank roof drains, inadequately dried equipment, etc.) all of these must be either designed out or be very well managed via operating and maintenance procedures. 

The analysis of the composite sample from the same series of curium-americium oxide production runs is presented in Table II. The content of carbon, the major impurity, is inferred rather than directly analyzed. The analyses of curium-americium oxide products generally reflect the purity of the feed, except for carbon and sulfur from the resin and a few potential corrosion products. 

X-ray photoelectron spectroscopy (XPS), also called electron spectroscopy for chemical analysis (ESCA), is a useful measure to know chemical environment of elements in material surface. The strength of XPS is its ability to identify different chemical states. This function is useful in physics, chemistry and material science, such as oxidation/corrosion products, adsorbed species or thin-film growth processes. Analysis of insulators is possible, and XPS is also capable of semiquan-titative analysis. 

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