铝合金材料工厂认可时，多家船级社均提出了金相组织与耐腐蚀性能的相关性试验要求，但很多制造商的铝合金常规试验中未开展此类相关性分析，本文根据咨询经验，为各位相关用户提供一个落地方案。下面就DNVGL船级社的要求开展分析及落地。

　　第一节：DNVGL认可要求

　　ReLationship between microstructure and resistance to corrosion(if applicable)

　　— for plates that require exfoliation and inter-granular corrosion the manufacturer shall establish the relationship between microstructure and resistance to corrosion

　　— a reference photomicrograph taken at 500x, under the conditions specified in ASTM B928, 9.4.1 shall be established for each of the alloys for each of the applicable tempers and for each thickness ranges as

　　relevant. The reference photographs shall be taken from samples which have exhibited no evidence of exfoliation corrosion and a pitting rating of PB or better, when subjected to the test described in ASTM G66 (ASSET). The samples shall also have exhibited resistance to inter-granular corrosion at a mass loss no greater than 15 mg/cm2, when subjected to the test described in ASTM G67

　　— upon satisfactory establishment of the relationship between microstructure and resistance to corrosion, the reference photomicrographs and the results of the corrosion tests shall be approved by the Society

　　— production practices shall not be changed after approval of the reference micrographs.

　　第二节：落地措施

　　一、建立金相组织与耐腐蚀性能相关作业文件

　　当制造商日常开展了5083,5383,5059,5086,5456的H116或H321状态下的金相组织分析，晶间腐蚀及剥落腐蚀试验时，可以根据这些历史数据建立相应的作业指导书，建立每种牌号、不同制造方式(冷轧/热轧)及状态(H116，H321)产品的金相组织与耐腐蚀性对应关系。

　　二、建立金相组织与耐腐蚀性能分析报告

　　本文推荐使用该种方式，适用于建立数据库不完善的广大铝合金制造商：

　　1、在提交型式试验大纲时，在5083,5383,5059,5086,5456的H116或H321状态产品的试验项目下提报一个金相组织与耐腐蚀性能分析项目：

　　2、规定金相分析、晶间腐蚀、剥落腐蚀试验要求;

　　Metallographic examination金相分析

　　Specimen shall be sampled at the mid-wall thickness of the test block. The test block shall be made from mid width of the product, at one end of plates.

　　金相试样应取自1/2厚度。试样应从板材一端的1/2宽度位置截取。

　　For rolled plates: a longitudinal section perpendicular to the rolled surface shall be prepared. The microstructure shall be compared to the reference photomicrograph of acceptable material.

　　对于轧制板材，试样的纵向界面垂直于板材轧制面。显微组织照片应在报告中体现，并能作为材料接收准则的依据。

　　High quality photomicrographs showing the microstructure at 100x and 500x magnification shall be prepared with a brief description. The magnification shall be indicated on the micrographs by a line symbol, e.g. with length of 0.5 mm or 100 μm. Arrows or letters may be used to identify features referred to in the report.

　　100x和500x的清晰照片和简单的描述需要在报告中体现。照片中包含线性标尺符号，如0.5 mm或100 μm长度的标尺。为了识别特征箭头或字母可以在报告中使用。

　　IntergranularCorrosion晶间腐蚀

　　1 Rolled 5000 series alloys of grade 5083, 5383, 5456 and 5086 in the H116 and H321 tempers intended for use in marine hull construction or in marine applications where frequent direct contact with seawater is expected shall be tested with respect to inter-granular corrosion resistance.用于船体机构或海工应用于平凡接触海水的热处理状态H116, H321的5083, 5383, 5456和5086应进行晶间腐蚀试验。

　　2 Measure all three dimensions to the nearest 0.02 mm, and calculate the total surface area.测量所有的三个尺寸精确到0.02mm，并计算总表面积。

　　3 Immerse the specimens in 5 % NaOH solution at 80°C for 1 min followed by a water rinse, a 30-s immersion in HNO3(desmut), and a water rinse. Allow the specimens to air dry. Do not wipe dry with a cloth or paper towel.将试样浸入到80℃，5%NaOH溶液中1分钟，然后用水冲洗。再将试样浸入到硝酸溶液中30秒，然后用水冲洗。将试样在空气中晾干。不允许用布或纸巾将试样擦干。

　　4 Weigh the specimens to no more than±1.0 mg, preferably 0.1 mg.称量试样至两次不超过±1.0 mg，精确至0.1mg。

　　5 Use sufficient test solution to fully immerse the specimens and constitute a volume to specimen surface area ratio of at least 30 L/m2. Maintain the test solution temperature at 30±0.1°C. Immerse the specimens in the test solution for 24 h.将使用完全浸入到试验溶液中。溶液体积与试样表面积比率不小于30L/m2。保持试验溶液温度为30±0.1°C。浸蚀时间为24h。

　　6 Remove the specimens, and rinse with water while brushing with a stiff plastic bristle brush, for example, a toothbrush, to remove all adhering particles. Allow to air dry.将试样取出用水冲洗并用硬所料毛刷刷洗，除去所有附着微粒，然后在空气中晾干。

　　7 Weigh the specimens and determine mass losses. In case of testing in accordance with ASTM G67 the mass loss shall not exceed 15 mg/cm2.称量试样重量并计算重量损失率。按ASTM G67试验的重量损失率不大于15 mg/cm2.

　　Exfoliation Corrosion剥落腐蚀

　　1 Rolled 5000 series alloys of grade 5083, 5383, 5456 and 5086 in the H116 and H321 tempers intended for use in marine hull construction or in marine applications where frequent direct contact with seawater is expected shall be tested with respect to exfoliation corrosion resistance.用于船体机构或海工应用于平凡接触海水的热处理状态H116, H321的5083, 5383, 5456和5086应进行剥落腐蚀试验。

　　2 Degrease the specimens with a suitable solvent. After degreasing, prepare specimens as follows: Etch 1 min in 5 % by weight sodium hydroxide solution at 80°C, rinse in water, desmut 30 s in concentrated nitric acid at room temperature, rinse with distilled or deionized water, air dry.用适当的溶剂给试样脱脂。脱脂后,准备样本如下:用重量百分含量在5%的氢氧化钠溶液在80°C蚀洗1分钟，清水冲洗，再在室温下的浓硝酸中30s,用蒸馏或去离子水,洗净晾干。

　　3 Use fresh solution at the start of each test.每次实验前更换新的溶液。

　　4 Immerse the specimens vertically with the top edge of the specimens at least 25 mm (1 in.) below the surface of the solution and the bottom edge at least 25 mm above the bottom of the container.把试样完全浸没在试验溶液中，溶液面在垂直方向上至少在试样上表面25mm以上，试样下表面离容器底部25mm。

　　5 Immerse the specimens in the test solution continuously for 24 h.把试样浸没在试验溶液中24h。

　　6Rinse the specimens gently in running tap water immediately after removal from the solution, then soak in concentrated nitric acid at room temperature until they appear clean, again rinse in water, and air dry.但把试样从试验溶液中拿出来后在流动的水中冲洗，然后放在洪硝酸中清洗至表面干净位置，然后用水冲洗，空干。

　　7 Air-blast drying is to be avoided in order to prevent mechanical removal of exfoliated metal.用吹风机吹干试样以防止机械性的操作到时剥脱金属的掉落。

　　8 Accepted test standards are ASTM G66 (ASSET). The indices for exfoliation corrosion shall be within the level EA and those for crevice corrosion rate shall be within PB according to ASTM G66.试验标准为ASTM G66 (ASSET)，剥落腐蚀的指标小于EA级，缝隙腐蚀率在PB级以内。。

　　3、建立金相组织与耐腐蚀性分析报告。

　　根据规定的牌号及状态下型式试验产品的金相分析结果、晶间腐蚀及剥落腐蚀试验结果建立如下分析报告。

　　4、规定在工艺条件不变的情况下，后期产品检验可以用金相分析代替耐腐蚀性能试验。