Metal Finishing Guide Book

2012-2013

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troubleshooting, testing, & analysis ACCELERATED CORROSION TESTING BY RAYMUND SINGLETON SINGLETON CORP., CLEVELAND Accelerated corrosion testing of metals and coatings was first developed in the late 1890s and early 1900s for testing products to increase their useful performance and service life. This method of testing the corrodibility of ferrous and nonferrous metals and organic and inorganic coatings has since been improved and variations added to better test new materials and help operators understand how they may perform in, and withstand, a wider range of real world environments. Accelerated corrosion testing has also evolved from providing information to help determine durability of products, and their quality assurance during manufacturing, to use in product research and development. Professional trade, industry, military and standards organizations, such as: ASTM International (American Society for Testing and Materials), the Society of Automotive Engineers (SAE), the Federation of Societies for Coatings Technologies (FSCT), NACE International (National Association for Corrosion Engineers ), Society for Protective Coatings (SSPC) and others have developed a number of accelerated corrosion tests to meet the demands of changes, and advances, in technology, materials, and other performance requirements and environmental regulations. For instance, water-based coatings have been developed as replacements for solvent-based liquid coating materials in response to environmental concerns. Some powder coatings and their application methods reduce the use of solvents and ease application. In addition, the automotive industry has improved coatings and increased the number of surfaces coated as part of the response to market pressures for longer warranties. Some of the more widely used tests are the representative ASTM Standards detailed in this article and well known industry cyclic corrosion tests such as: General Motors GMW14872 (formerly GM9540P), and SAE J2334. There are many other tests in use; however, those mentioned also exhibit wider applicability and versatility and are, therefore, some of the more popular procedures. Other than the ASTM B117 Salt Fog test, most widely used for on-line process and product quality control, no other single corrosion test is as dominant because of the wide variety of service conditions, product industries and specific issues such as various materials, applications methods, properties, and varying surfaces. Other considerations to consider when choosing or specifying a particular accelerated corrosion test include the multitude of environments and customer demands faced by a product and industry. A variety of standard tests has been developed to address these issues. One of the first���and still most widely utilized���accelerated corrosion tests developed is ASTM B117 Operating Salt Spray (Fog) Apparatus. Early development of corrosion tests was initiated in order to evaluate the corrodibility of metals and protective properties of coatings in a marine or ���near shore��� environment. As corrosion testing was increasingly used also to evaluate product quality and materials used in product development, variations on the basic, or original, corrosion test standards have been added to increase their usefulness for a wider range of environments and materials. This process has resulted in the development of the various representative accelerated corrosion tests to be discussed in this article. 589

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