1.1 本指南介绍了估算低合金耐候钢耐大气腐蚀性的两种方法，如规范中所述 A242/A242M , A588/A588M , A606/A606M 类型4， A709/A709M 50W、HPS 70W和100W级， A852/A852M 和 A871/A871M . 一种方法是根据短期试验结果，估计特定地点钢材的长期厚度损失。另一种是根据化学成分估算相对耐腐蚀性。 1.2 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.3 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 过去，ASTM规范适用于低合金耐候钢，例如 A242/A242M , A588/A588M , A606/A606M 类型4， A709/A709M 50W、HPS 70W和100W级， A852/A852M 和 A871/A871M 声明称，这些钢的耐大气腐蚀性“大约是含铜碳素结构钢的两倍”规范中的脚注指出，“含铜的两倍碳结构钢相当于不含铜的四倍碳结构钢（铜最大值为0.02）。”因为将耐候钢的耐腐蚀性与其他钢的耐腐蚀性联系起来的此类陈述不准确，更重要的是，对用户来说缺乏意义 ( 1和 2. ) , 4. 本指南旨在描述估算耐候钢耐大气腐蚀性的更有意义的方法。 5.2 本指南的第一种方法旨在估算特定等级的低碳钢的预期长期大气腐蚀损失- 各种环境中的合金钢，利用这些等级钢的现有短期大气腐蚀数据。 5.3 本指南的第二种方法旨在根据低合金钢的化学成分估算其比热的相对大气耐腐蚀性。 5.4 重要的是要认识到，本文提出的方法是基于根据平坦、大胆暴露的钢试样的试验数据进行的计算。当耐候钢长时间保持潮湿，或被盐或其他腐蚀性化学品严重污染时，大气腐蚀速率可能会更高。因此，在应用这些方法预测实际结构的长期性能时必须谨慎。

1.1 This guide presents two methods for estimating the atmospheric corrosion resistance of low-alloy weathering steels, such as those described in Specifications A242/A242M , A588/A588M , A606/A606M Type 4, A709/A709M grades 50W, HPS 70W, and 100W, A852/A852M , and A871/A871M . One method gives an estimate of the long-term thickness loss of a steel at a specific site based on results of short-term tests. The other gives an estimate of relative corrosion resistance based on chemical composition. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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. ====== Significance And Use ====== 5.1 In the past, ASTM specifications for low-alloy weathering steels, such as Specifications A242/A242M , A588/A588M , A606/A606M Type 4, A709/A709M Grade 50W, HPS 70W, and 100W, A852/A852M , and A871/A871M stated that the atmospheric corrosion resistance of these steels is “approximately two times that of carbon structural steel with copper.” A footnote in the specifications stated that “two times carbon structural steel with copper is equivalent to four times carbon structural steel without copper (Cu 0.02 maximum).” Because such statements relating the corrosion resistance of weathering steels to that of other steels are imprecise and, more importantly, lack significance to the user ( 1 and 2 ) , 4 the present guide was prepared to describe more meaningful methods of estimating the atmospheric corrosion resistance of weathering steels. 5.2 The first method of this guide is intended for use in estimating the expected long-term atmospheric corrosion losses of specific grades of low-alloy steels in various environments, utilizing existing short-term atmospheric corrosion data for these grades of steel. 5.3 The second method of this guide is intended for use in estimating the relative atmospheric corrosion resistance of a specific heat of low-alloy steel, based on its chemical composition. 5.4 It is important to recognize that the methods presented here are based on calculations made from test data for flat, boldly exposed steel specimens. Atmospheric corrosion rates can be much higher when the weathering steel remains wet for prolonged periods of time, or is heavily contaminated with salt or other corrosive chemicals. Therefore, caution must be exercised in the application of these methods for prediction of long-term performance of actual structures.