exposure likely will not produce enough corrosion activity to evaluate the corrosion behavior of the material. Nevertheless, by simulating the exact conditions of operation, an accurate assessment of the material can generally be produced with an adequate exposure time ASTM publishes standard test methods and analytical procedures for corrosion and wear testing (Ref 2) Electrochemical testing is performed for general information regarding the passivity or anodic protection of material against corrosion and to determine the critical breakdown or pitting potential. This type of testing is performed by two methods: controlling the current or controlling the potential. Standard methods for electrochemical testing are published in Ref 2 As the name suggests in the controlled-current test method the current is controlled and the resulting corrosion potential is measured. Polarization curves are generated. Galvanostatic and galvanodynamic polarization measurements are used to plot anodic and cathodic polarization curves. The assumption that corrosion rates remain constant with time can produce inaccurate results with this test method In the controlled-potential method, instrumentation is available for both constant-potential(potentiostatic)and variable-potential(potentiodynamic) testing to determine overall corrosion-rate profiles for metal-electrolyte stems over a range of potentials Corrosion Rates and Types. Knowing and understanding corrosion rates and the types of corrosion is essential to the evaluation of corrosion failures and to the communication of the results to others the articles that follow in this Section discuss the forms mechanisms and relative rates of corrosion. Corrosion Volume 13 of the ASM Handbook, provides detailed information regarding types of corrosion, corrosion testing, corrosion failures, and industry- and alloy-Specific corrosion considerations. Volume 13 also provides information regarding the use of specific alloys in given environments, corrosion prevention, and the use of nonmetallic materials. The Handbook of Corrosion Data, 2nd edition(ASM International, 1995)is a compilation of corrosion data from published sources. Corrosion rates of various alloys are provided with a general discussion of the corrosion resistance of alloy groups in particular environments Internet web sites published by ASM International, ASTM, NACE, the Nickel Development Institute, and the Copper Development Association provide the ability to search libraries of data for a given request Analysis of Incomplete Data. Incomplete or inconsistent data may occur in certain instances when the failure piece has been contaminated by an unknown source. Improper handling of the failure sample can introduce contamination on the sample. Testing of contaminated samples may produce misleading data and erroneous results. For example, the sampling of a deposit removed from a fracture surface that experienced stress corrosion may not reveal the corrodent that caused the scc. often the fracture surface is flushed with water or cleaned prior to testing. Liquid penetrants, cleaning fluids, cutting fluids, and solvents may alter the chemical composition of the surface deposits Results from laboratory testing may provide extraneous results. The tests may not model the service conditions Laboratory testing cannot easily model flow conditions such as turbulence, erosion, and localized attack. Care must be taken when evaluating the laboratory data to be certain that the conclusions drawn are an accurate assessment of the operating environment ASTMG 16, "Applying Statistics to Analysis of Corrosion Data"(Ref 3), provides a guide for handling data; it refers to ASTM E 178, Practice for Dealing with Outlying Observations"(Ref 4) for the treatment of data that appear inconsistent with the bulk of the findings References cited in this section 2. Wear and Corrosion, Vol 03.02, Annual Book of AsTM Standards, ASTM 3.Applying Statistics to Analysis of Corrosion Data, G 16, Annual Book of ASTM Standards, ASTM 4."Practice for Dealing with Outlying Observations, " E 178, Annual Book of ASTM Standards, ASTM Thefileisdownloadedfromwww.bzfxw.comexposure likely will not produce enough corrosion activity to evaluate the corrosion behavior of the material. Nevertheless, by simulating the exact conditions of operation, an accurate assessment of the material can generally be produced with an adequate exposure time. ASTM publishes standard test methods and analytical procedures for corrosion and wear testing (Ref 2). Electrochemical testing is performed for general information regarding the passivity or anodic protection of a material against corrosion and to determine the critical breakdown or pitting potential. This type of testing is performed by two methods: controlling the current or controlling the potential. Standard methods for electrochemical testing are published in Ref 2. As the name suggests, in the controlled-current test method, the current is controlled and the resulting corrosion potential is measured. Polarization curves are generated. Galvanostatic and galvanodynamic polarization measurements are used to plot anodic and cathodic polarization curves. The assumption that corrosion rates remain constant with time can produce inaccurate results with this test method. In the controlled-potential method, instrumentation is available for both constant-potential (potentiostatic) and variable-potential (potentiodynamic) testing to determine overall corrosion-rate profiles for metal-electrolyte systems over a range of potentials. Corrosion Rates and Types. Knowing and understanding corrosion rates and the types of corrosion is essential to the evaluation of corrosion failures and to the communication of the results to others. The articles that follow in this Section discuss the forms, mechanisms, and relative rates of corrosion. Corrosion, Volume 13 of the ASM Handbook, provides detailed information regarding types of corrosion, corrosion testing, corrosion failures, and industry- and alloy-specific corrosion considerations. Volume 13 also provides information regarding the use of specific alloys in given environments, corrosion prevention, and the use of nonmetallic materials. The Handbook of Corrosion Data, 2nd edition (ASM International, 1995) is a compilation of corrosion data from published sources. Corrosion rates of various alloys are provided with a general discussion of the corrosion resistance of alloy groups in particular environments. Internet web sites published by ASM International, ASTM, NACE, the Nickel Development Institute, and the Copper Development Association provide the ability to search libraries of data for a given request. Analysis of Incomplete Data. Incomplete or inconsistent data may occur in certain instances when the failure piece has been contaminated by an unknown source. Improper handling of the failure sample can introduce contamination on the sample. Testing of contaminated samples may produce misleading data and erroneous results. For example, the sampling of a deposit removed from a fracture surface that experienced stress corrosion may not reveal the corrodent that caused the SCC. Often the fracture surface is flushed with water or cleaned prior to testing. Liquid penetrants, cleaning fluids, cutting fluids, and solvents may alter the chemical composition of the surface deposits. Results from laboratory testing may provide extraneous results. The tests may not model the service conditions. Laboratory testing cannot easily model flow conditions such as turbulence, erosion, and localized attack. Care must be taken when evaluating the laboratory data to be certain that the conclusions drawn are an accurate assessment of the operating environment. ASTM G 16, “Applying Statistics to Analysis of Corrosion Data” (Ref 3), provides a guide for handling data; it refers to ASTM E 178, “Practice for Dealing with Outlying Observations” (Ref 4) for the treatment of data that appear inconsistent with the bulk of the findings. References cited in this section 2. Wear and Corrosion, Vol 03.02, Annual Book of ASTM Standards, ASTM 3. “Applying Statistics to Analysis of Corrosion Data,” G 16, Annual Book of ASTM Standards, ASTM 4. “Practice for Dealing with Outlying Observations,” E 178, Annual Book of ASTM Standards, ASTM The file is downloaded from www.bzfxw.com