【国外标准】 Standard Test Method for Determination of Corrosion Rate in a Water System in the Absence of Heat Transfer (Weight Loss Method)

4.1 Since the two tendencies are inseparable for a metal to corrode and for water and the materials it contains to promote or inhibit corrosion, the corrosion rate of a material in water is determined in relative, rather than absolute, terms. The relative tendency for a material to corrode is determined by measuring its rate of corrosion and comparing it with the corrosion rates of other materials in the same water environment. Conversely, the relative tendency of water to promote or inhibit corrosion can be determined by comparing the corrosion rate of a material in the water with the corrosion rates of the same material in other waters. Such tests are useful, for example, for evaluating the effects of corrosion inhibitors added to the water. Examples of systems in which this method can be used include, but are not limited to, open recirculating cooling water, closed chilled water, and hydronic heating systems.1.1 This test method covers the determination of the corrosion rate in a water system, in the absence of heat transfer.1.1.1 This is accomplished by measuring the weight loss of metal specimens, also called coupons, and evaluating pitting. Weight loss provides the means to calculate the average corrosion rate. Pitting is a form of localized corrosion.1.1.2 The rate of corrosion of a metal immersed in water is a function of both the characteristics of the water itself and the materials it contains to promote or inhibit corrosion.1.2 The test method employs flat, rectangular-shaped metal coupons which are mounted on pipe plugs and exposed to the water flowing in piping in municipal, building, and industrial water systems using a side stream corrosion specimen rack.1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.