1.1 本指南涵盖了绝缘下腐蚀（CUI）的模拟，包括对从暴露于通常在高温下的腐蚀环境中的管段上切割的绝缘试样的一般和局部腐蚀。它描述了CUI暴露装置（以下简称CUI电池）、试样制备、等温或循环温度的模拟程序，或两者，以及湿/干条件，这些是模拟期间需要监测的参数和模拟类型的分类。 1.2 本指南的应用范围很广，可以包含一系列超出单一测试方法范围的材料、环境和条件。 本文中包含的设备和程序主要旨在建立可接受的CUI模拟程序，以评估CUI环境对碳钢和低合金钢的腐蚀性，并可能适用于其他材料。然而，同样或类似的程序也可用于评估 (1) 其他金属或合金， (2) 金属表面的防腐处理，以及 (3) 隔热材料及其成分对CUI的潜在贡献。唯一的要求是可以将其加工、成型或合并到CUI中- 如本文所述的电池管配置。 1.3 以英寸-磅为单位的数值应视为标准值。括号中给出的值是到国际单位制的数学转换，仅供参考，不被视为标准值。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 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 在钢和其他隔热材料上观察到的腐蚀是许多行业非常关注的问题，包括化工、炼油和发电。 在大多数情况下，管道和容器上使用保温材料来维持操作系统的温度，以实现过程稳定和节能。然而，这些情况也可能为发生一般腐蚀或局部腐蚀或两者兼有以及不锈钢应力腐蚀开裂提供先决条件。例如，结合高温，CUI有时会导致钢的水腐蚀速率大于在开放或封闭系统中进行的传统浸入试验中发现的腐蚀速率（参见 图1 ). 3. 该图显示了现场确定的实际CUI数据，与全浸腐蚀试样测试的腐蚀数据进行了比较。 图1 实际电厂CUI腐蚀速率测量值（所示的开放数据点用于电厂CUI）与在开放和封闭系统中获得的实验室腐蚀数据的比较 注1: 实际CUI腐蚀速率可能超过在常规实验室浸没暴露中获得的腐蚀速率。 5.2 本指南为崔的许多表现形式的实验室模拟提供了技术基础。 这是一个需要更好的模拟技术的领域，但直到最近，许多研究人员还没有找到。许多可用的实验数据基于剩余壁厚的现场和厂内测量。实验室研究通常仅限于使用与指南中给出的技术类似的技术，对腐蚀试样上隔热层的浸出剂的腐蚀性进行简单的浸泡试验 G31 . 现场和厂内测试表明腐蚀发生后，不容易用于实验目的。 在实验室浸没试验中使用试样可以给出腐蚀趋势的一般指示。然而，在某些情况下，这些程序有助于根据绝缘材料浸出腐蚀性物质的倾向对其进行排序。然而，由于暴露几何形状、温度、循环温度或工厂和现场环境中的湿/干条件的差异，这种浸入技术并不总是准确地表示在服务中经历的实际CUI趋势。 5.3 本文所含装置和方法的一个特殊方面是其适应对成功模拟CUI暴露条件至关重要的几个方面的能力。 这些是: (1) 管道和周围隔热层之间的理想环形几何形状， (2) 内部加热以产生热壁表面，在该表面上可以量化CUI， (3) 将离子溶液引入管道和隔热层之间的环形空腔， (4) 控制温度以产生等温或循环温度条件，以及 (5) 控制交付控制或溶液以产生湿或干湿条件。其他更简单的方法可用于对浸入各种溶液和热绝缘浸出剂中的试样进行腐蚀评估。 在某些情况下，这些程序可用于评估各种因素对腐蚀的影响。然而，它们不能适应CUI模拟可能需要的上述因素。 5.4 使用CUI单元，可以为所需的模拟选择管道材料、隔热层和环境。因此，无法定义单一的标准暴露条件。本指南旨在帮助实验室模拟 (1) 不同绝缘材料对CUI的影响，在某些情况下，可能包含加速腐蚀的材料或添加剂，或两者兼有， (2) 应用或以其他方式加入抑制剂或保护涂层对降低CUI程度和严重性的影响。本指南在相对较短的时间（约72小时）内提供了有关CUI的信息，并提供了一种评估腐蚀速率随时间和环境条件变化的方法。

1.1 This guide covers the simulation of corrosion under insulation (CUI), including both general and localized attack, on insulated specimens cut from pipe sections exposed to a corrosive environment usually at elevated temperature. It describes a CUI exposure apparatus (hereinafter referred to as a CUI-Cell), preparation of specimens, simulation procedures for isothermal or cyclic temperature, or both, and wet/dry conditions, which are parameters that need to be monitored during the simulation and the classification of simulation type. 1.2 The application of this guide is broad and can incorporate a range of materials, environments and conditions that are beyond the scope of a single test method. The apparatus and procedures contained herein are principally directed at establishing acceptable procedures for CUI simulation for the purposes of evaluating the corrosivity of CUI environments on carbon and low alloy pipe steels, and may possibly be applicable to other materials as well. However, the same or similar procedures can also be utilized for the evaluation of (1) CUI on other metals or alloys, (2) anti-corrosive treatments on metal surfaces, and (3) the potential contribution of thermal insulation and its constituents on CUI. The only requirements are that they can be machined, formed or incorporated into the CUI-Cell pipe configuration as described herein. 1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI 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. ====== Significance And Use ====== 5.1 The corrosion observed on steel and other materials under thermal insulation is of great concern for many industries including chemical processing, petroleum refining and electric power generation. In most cases, insulation is utilized on piping and vessels to maintain the temperatures of the operating systems for process stabilization and energy conservation. However, these situations can also provide the prerequisites for the occurrence of general or localized corrosion, or both, and in stainless steels, stress corrosion cracking. For example, combined with elevated temperatures, CUI can sometimes result in aqueous corrosion rates for steel that are greater than those found in conventional immersion tests conducted in either open or closed systems (see Fig. 1 ). 3 This figure shows actual CUI data determined in the field compared with the corrosion data from fully immersed corrosion coupons tests. FIG. 1 Comparison of Actual Plant CUI Corrosion Rates Measurements (Open Data Points Shown is for Plant CUI) with Laboratory Corrosion Data Obtained in Open and Closed Systems Note 1: The actual CUI corrosion rates can be in excess of the those obtain in conventional laboratory immersion exposures. 5.2 This guide provides a technical basis for laboratory simulation of many of the manifestations of CUI. This is an area where there has been a need for better simulation techniques, but until recently, has eluded many investigators. Much of the available experimental data is based on field and in-plant measurements of remaining wall thickness. Laboratory studies have generally been limited to simple immersion tests for the corrosivity of leachants from thermal insulation on corrosion coupons using techniques similar to those given in Guide G31 . The field and inplant tests give an indication of corrosion after the fact and can not be easily utilized for experimental purposes. The use of coupons in laboratory immersion tests can give a general indication of corrosion tendencies. However, in some cases, these procedures are useful in ranking insulative materials in terms of their tendencies to leach corrosive species. However, this immersion technique does not always present an accurate representation of the actual CUI tendencies experienced in the service due to differences in exposure geometry, temperature, cyclic temperatures, or wet/dry conditions in the plant and field environments. 5.3 One of the special aspects of the apparatus and methodologies contained herein are their capabilities to accommodate several aspects critical to successful simulation of the CUI exposure condition. These are: (1) an idealized annular geometry between piping and surrounding thermal insulation, (2) internal heating to produce a hot-wall surface on which CUI can be quantified, (3) introduction of ionic solutions into the annular cavity between the piping and thermal insulation, (4) control of the temperature to produce either isothermal or cyclic temperature conditions, and (5) control of the delivery of the control or solution to produce wet or wet-dry conditions. Other simpler methods can be used to run corrosion evaluations on specimens immersed in various solutions and leachants from thermal insulation. In some cases, these procedures may be acceptable for evaluation of the contribution of various factors on corrosion. However, they do not provide accommodation of the above mentioned factors that may be needed for CUI simulation. 5.4 With the CUI-Cell, the pipe material, insulation and environment can be selected for the desired simulation needed. Therefore, no single standard exposure condition can be defined. The guide is designed to assist in the laboratory simulation of (1) the influence of different insulation materials on CUI that, in some cases, may contain materials or additives, or both, that can accelerate corrosion, (2) the effect of applied or otherwise incorporated inhibitors or protective coatings on reducing the extent and severity of CUI. This guide provides information on CUI in a relatively short time (approximately 72 h) as well as providing a means of assessing variation of corrosion rate with time and environmental conditions.