CORROSION TESTS ARE performed to provide information on material degradation in specific environments, information that is not available from other sources. Corrosion testing can be divided into two broad categories, electrochemical and nonelectrochemical. Within these categories, test results are presented in a number of ways, ranging from numerical output to qualitative examination of the test specimen. Both types of data are represented in each category. A very complete listing of data formats for collection and compilation for computerized databases is presented in ASTM G 107, Guide for Formats for Collection and Compilation of Corrosion Data for Metals for Computerized Database Input. The information in that standard includes a significant portion of the type of test data that might be recorded during corrosion testing. Since required data are test-dependent, not every test would include all of the data listed, but the standard does provide a reasonable, first pass checklist and should be used to ensure that needed information is not overlooked.
BECAUSE CORROSION is fundamentally a surface phenomenon, those interested in the fundamental processes of corrosion have always been among the first to explore the utility of surface analysis techniques. These techniques have had, and will continue to have, great success in illuminating many facets of corrosion phenomena.
THE AUTOMOTIVE INDUSTRY has become one of the key sectors of the economy throughout the world. In industrialized countries it is estimated that between 10 and 16 % of the working population is employed in activities related to the automotive sector.
FAILURE IN ELECTRONICS DUE TO corrosion has become a significant factor because of the extremely complex systems (microchips, integrated circuits, computers, et cetera) that have been developed and the increasing demand on their reliability. Electronics are now a part of all industries, ranging from transportation industries to medical and consumer products. Technological advances have resulted in the development of sophisticated components with closer spacing so that extremely low levels of corrosive contaminants can cause failure. Testing for this type of behavior is difficult and costly. Further advances in electronics can only be made where corrosion issues are addressed and reliability is maintained. Many publications have appeared in the technical literature on the subject of corrosion in electronics with more and more emphasis on testing [1-10].
MOST PHYSICAL AND CHEMICAL measurements, performed under nominally identical conditions, yield differing data. The results of corrosion tests are no exception. Sometimes the difference between values is less than the measurement accuracy and cannot be detected. At other times the difference approaches the magnitude of the values. Unfortunately, corrosion test data tend to be in the latter category more often than in the former.
CORROSION TESTS ARE an important tool for evaluating the performance of materials used in scientific, industrial, engineering, consumer, and aesthetic applications, where corrosion was estimated to cost the U.S. economy.
COMPUTERS PLAY IMPORTANT roles in data acquisition in laboratory and field environments, data processing and analysis, data searching and data presentation in understandable and useful formats. The rapid development of accessible computing power since the 1980s has led to the use of computers and direct or indirect applications of machine intelligence in every sphere of science and engineering. As a modern science philosopher has written, The emergence of machine intelligence during the second half of the twentieth century is the most important development in the evolution of this planet since the origin of life two to three thousand million years ago. Computers also assist engineers to transform data into usable and relevant information. The connectivity of computers to the outside world through the Internet and the Web has opened up tremendous channels of communication that never existed before.
A NEW DOOR opened into the study of materials in the late 19th century (1863) when a British geologist named Henry C. Sorby decided to polish a piece of steel, etch it with acid, and examine it under a microscope. Since that time, metallographic examinations have been performed on most every engineering material developed.
IN MOST INSTANCES, corrosion test methods for plain carbon steels, high-strength low-alloy steels, and alloy steels do not differ greatly. Therefore, these steels are grouped together for the purposes of this chapter. (Alloy steels here refers to heat treatable constructional and automotive steels, and does not include the stainless steels or other high alloys.) There are some differences in the corrosion test methods used for different mill products of this group of steels, and these will be discussed. The steels covered in this chapter are defined below.
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