Corrosion tests industrial chemicals

Potokar M, Grundler OJ, Heusener A, et al. 1985. Studies on the design of animal tests for the corrosiveness of industrial chemicals. Food Chem Toxicol 23(6) 615-617. 

The successful application of nickel-chromium-iron alloys as structural components of industrial furnaces and as chambers and containers in chemical processing under conditions of exposure involving sulphur substantiates their good resistance to this form of corrosion. These materials are used for service temperatures in the range 750-1 200°C, the upper limit of serviceability being determined largely by the chromium content of a particular alloy. Results of corrosion tests (Table 7.24) on cast nickel-... 

The Materials Technology Institute of the Chemical Process Industry (MTI) has identified five corrosion tests for iron- and nickel-based alloys, out of which two concern the resistance to crevice corrosion. The method MTI-2, originating from ASTM G48, involves the use of 6% ferric chloride solution for determining the relative resistance of alloys to crevice corrosion in oxidizing chloride environment. The method MTI-4 uses an increase in neutral bulk Cl- concentration at eight levels, ranging from 0.1 to 3% NaCl, to establish the minimum critical Cl concentration that produces crevice corrosion at room temperature (20-24°C).43,44... 

Furan polymer concrete is a corrosion-resistant polymer material. Endurance tests (a year or more) showed high resistance of this material to most industrial chemicals, except oxidants (nitric acid, acetic acid) and some solvents (acetone, benzene, alcohol). 

Plastic materials are quite effective in controlling corrosion in industrial processing and storage. In a variety of applications, plastics are the only acceptable choice for process surfaces because of their chemical inertness. In each case, plastics must be qualified by testing to insure adequate corrosion protection and compliance with ever more stringent environmental and safety regulations. 

Apart from the variety of possible agent fills, there are several other reasons why unusual compounds might be present in recovered munitions. Special formulations of agents and industrial chemicals were sometimes used to achieve certain effects. For instance, tin tetrachloride was encountered in phosgene rounds treated in the Porton Down tests of the EDS-1. This chemical was added to facilitate the penetration of gas masks and to produce a smoke that aided in spotting where rounds had landed. Chlorobenzene, possibly used as a solvent or stabilizer, was found in the mustard rounds processed at Porton Down (Table 2-1). Chlorinated rubber was used as a thickener in some mustard formulations. In addition, unusual compounds or sludges may result from chemical reactions such as corrosion and polymerization that may occur among the components over a period of decades. 

Horton et al. [55] observed that when steels containing Cu and Ni are exposed in industrial and marine atmospheres, the Cu and Ni appear in the mst layers both in the loose outer and adherent inner mst on skyward and ground ward surfaces. Also it was shown by chemical analysis that Ni, Cu, Cr and Mn from weathering steel appear in the mst layer and provides protection. Presence of chlorides in the atmosphere accelerates corrosion of steels leading to the formation of basic Fe ", Fe chlorides and jS FeOOH. Townsend et al. [56] conducted 8-year atmospheric corrosion tests on weathering steel in mral, industrial and marine environments with different heated conditions and indicated that heat treatments have no effect on the corrosion resistance/performance of weathering steels. 

Section V on Testing in Environments (H. Hack, Section Editor) includes chapters on outdoor and indoor atmospheres, seawater, fresh water, soils, concrete, industrial waters, industrial chemical, petroleum, high-temperature gases, organic liquids, molten salts, liquid metals, corrosion inhibitors, in-vivo, and microbiological effects. Each chapter provides a descriptive overview of the environment and factors and variables affecting corrosion rates and mechanisms. 

Failure analysis is an important aspect of corrosion testing since failed components inform the corrosionist about the severity of actual steady-state and transient operating conditions, improperly identified or selected materials, and faulty equipment design. Figure 4 outlines t5rpical steps in faflure analysis that are applicable to the CPI and other industries. At the heart of this process is testing to determine chemical, corrosion, and mechanical contributions to the failure and to validate the results of the analysis. Failure analysis is an effective means to lower maintenance costs and a strategy to limit risk to operational safety. 

Laboratory corrosion tests for exfoliation corrosion susceptibility are a necessary tool for research and quality control engineers however, the validity of such accelerated tests depends on their relationship to realistic service conditions and their sensitivity to various degrees of susceptibility. The tests must be discriminating and yet not so severe as to be unrealistic. For the majority of engineered structures, exposure to outdoor atmospheres provides a baseline that is representative of many service conditions, except for structures that are subjected to unusual chemical environments. Experience has shown that seacoast conditions are more corrosive to aluminum alloys than inland urban and industrial conditions (see Fig. 2), and seacoast atmospheric exposure tests have been particularly useful for the validation of accelerated exfoliation tests [9]. 

One variable frequently overlooked in designing tests for selecting materials for industrial chemical applications is the presence of small quantities of chemicals present as contaminants that is, chemicals that are there unintentionally. Often these chemicals have no effect on corrosion behavior and can be safely ignored. However, eJl too often this is not the case. Consider, for example, the effect of a few... 

Specific tests frequently used are (a) neutral 5 % Sodium Chloride salt spray (ASTM B 117, Test Method of Salt Spray (Fog) Testing), (b) 3.5 % Sodium Chloride by alternate immersion (ASTM G 44, Practice for Evaluating Stress Corrosion Cracking Resistance of Metals in 3.5 % Sodium Chloride Solution), and (c) exposure to various outdoor atmospheres. Guidelines for outdoor exposure are contained in ASTM G 50, Practice for Conducting Atmospheric Corrosion Tests on Metals. Generic types of atmospheres used are seacoast, industrial, urban, and rural. Sometimes specific geographical locations or local chemical conditions are important because they can produce unique results [2i],... 

There are many examples of the catastrophic role played by impurities in the process industries. Conventional corrosion data on sulfuric acid media, for example, are often based on tests in chemically pure acid or on field exposures of indeterminate chemistry and the effects of contaminants are often overlooked. Serious problems can therefore arise in seemingly straightforward applications [7]. 

Corrosion Monitoring in Industrial Plants Using Nondestructive Testing and Electrochemical Methods , Proc. Symposium Sponsored by ASTM Committee E-7 and G-1, Montreal, Canada, May 1984, ASTM Special Technical Publication 908 Internal Corrosion Control and Monitoring in the Oil, Gas and Chemical Industries Proc. 

Electrochemical On-Line Corrosion Monitoring On-line corrosion monitoring is used to evaluate the status of equipment and piping in chemical process industries (CPI) plants. These monitoring methods are based on electrochemical techniques. To use on-line monitoring effectively, the engineer needs to understand the underlying electrochemical test methods to be employed. This section covers many of these test methods and their applications as well as a review of potential problems encountered with such test instruments and how to overcome or avoid these difficulties. 

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