3.4          EXPOSURE CONDITIONS
3.4.1        General
3.4.1.1    Coating requirements are primarily determined by exposure conditions. The types and severity of exposures are outlined in the Appendices. The Appendices are to be used in selecting a coating system for facilities where conditions are expected to be similar to those shown in the charts.
3.4.1.2    Exposure conditions may overlap in a single location or a change in operation may bring a change of exposure conditions, either more or less severe.
3.4.2       Exposure Areas - Definitions
3.4.2.1     Severe Corrosive Areas (See Appendix 2.0)
This exposure shall be defined as any area where chemical fumes, mist or dust can combine with high humidity and condensed moisture to corrode carbon steel at rates greater than 150 micrometers per year and corrode zinc at rates greater than 25 micrometers per year. Local rates of pitting corrosion may be higher.
Other areas are equipment and surfaces operating above 66°C and subject to spills of corrosive materials.
Examples of areas where severe exposure conditions exist are sulphur plant areas, sulphur loading areas, chlorination units, areas within 15 m radius of cooling towers and areas with high concentrations of solvent and alkaline fumes.
3.4.2.2    Mild Corrosive Areas (See Appendix 2.1)
This area shall be defined as normal outdoor weathering and/or light concentrations of chemical fumes that combine with humidity and condensed moisture to corrode carbon steel at rates of 80 micrometers or less per year and zinc is almost free of corrosion.
Examples of mild corrosive areas are most tank farms, areas where moderate exposure conditions may be found and equipment operating at a temperature such that condensation forms on equipment externals (i.e., gas absorption units, refrigeration units, hot stacks and other surfaces subject to wide temperature fluctuations).

1.1.1 。

1.2 暴露条件
1.2.1 概述
1.2.1.1 喷涂施工的要求主要由暴露条件决定。材料的暴露形式和严重程度，在附录中进行了概述。可以利用附录，选择设施应采用的涂层系统，设施所处的环境，应与表中所列出的条件相当。

1.2.1.2 在独立的地点，暴露条件可能会相互交叉或随运行方式的改变而改变暴露条件，也许会加重材料的暴露，也许会降低材料的暴露。

1.2.2 暴露区域 － 定义
1.2.2.1 强腐蚀区域（见附录2.0）

暴露区域可以定义为：化学气体、雾气或灰尘可以与高湿度的空气混合，凝结成水分，并以每年大于150微米的速度腐蚀碳钢；以每年大于25微米的速度腐蚀锌。当地的孔蚀速度可能比这还要高。

其它区域是指设备和材料表面的运行温度在66℃以上，并受到了腐蚀性材料溢出的影响。

强腐蚀性暴露条件区域中有制硫车间、硫装载车间区域、加氯机附近、冷却塔15米半径以内，和有高浓度的溶剂和碱性气体存在的区域。

1.2.2.2 弱腐蚀区域（见附录2.1）

这一区域的定义是：正常的户外风化和／或空气中有较低的化学气体浓度，这些化学气体与水分结合，凝聚成水分，并以每年80微米以下的速度，腐蚀碳钢，而对锌则不具有腐蚀性。

弱腐蚀性区域包括多数的储油站，在这一区域中，暴露条件比较温和，设备运行温度较低，这样，凝露集中在设备的外表（亦即气体吸收装置、制冷装置、热的烟筒和其它表面上，而温度不会剧烈变动）。