【作者】 黄旋；

【导师】 刘秀生；

【作者基本信息】 机械科学研究总院 ， 材料学， 2012， 硕士

【摘要】 铝合金具有密度小、比强度高、耐蚀性和成型性好、成本低等优点，目前已成为飞机机体结构的主要用材，其用量高达60％～80％。然而，因多种因素导致其耐腐蚀性较差，为此大多航空铝合金部件需要钝化处理，以提高其耐蚀性能。传统的六价铬酸盐钝化具有高危害性和致癌性，必须开发六价铬钝化的替代工艺。三价铬毒性很低，与六价铬性能相似，是最有可能的替代技术。以2024、6061和7075三种铝合金为试验材料，研制出一种环保型的铝合金三价铬化学转化处理液，并对转化膜的性能及转化膜与漆膜的配套性进行了研究。本文以硫酸铬为主成膜物质，稀土金属盐为辅助成膜物质，通过单因素试验和正交试验，对化学转化液的主要成分及工艺条件进行了筛选，最终得到三价铬钝化液的最佳配方和工艺条件如下：硫酸铬0.010mol/L，稀土盐0.020mol/L，络合剂0.010mol/L，缓蚀剂0.025g/L；温度30～35℃，时间5min，pH值3.8～3.9。按照上述配方配置而成的钝化液为绿色透明液体，转化膜外观为均匀的浅蓝色。制备的三价铬化学转化膜各项性能优异，主要表现在：耐盐雾性能达到168h，耐蚀性远优于锆钛类无铬钝化膜，膜层表面连续完整，较Alodine1200处理得到的钝化膜更致密，电化学测试表明该三价铬钝化膜有着与六价铬钝化膜相当的耐蚀性，在三种铝合金上钝化膜膜重约在3～6mg/dm2之间，在此膜重范围内钝化膜与漆膜附着力良好，三价铬钝化膜对基材疲劳性能影响小，与Alodine1200钝化膜对比发现，对于2024铝合金，两种化学转化处理工艺的疲劳试验结果非常接近；对于7075铝合金，三价铬钝化膜的疲劳强度略高于Alodine1200工艺，二者在中、长寿命区的疲劳强度相差约8.5%。在转化膜表面喷涂航空底漆和面漆后，对其进行附着力、耐水性、耐油性、耐盐雾性能和耐湿热性能试验后表明，化学转化膜与漆膜配套性能优良。更多还原

【Abstract】 Aluminum alloy has many advantages, such as low density, high specific strength,good corrosion resistance and formability, low cost, etc. Nowadays it becomes the mainstructure materials of airframe, the amounts of it are up to60%～80%.However, due to avariety of factors, it has poor corrosion resistance, so most aerospace aluminum alloyparts need passivation to improve its corrosion resistance. Traditional hexavalentchromate passivation, has highly hazardous and carcinogenic, so it must develop analternative process to replace hexavalent chromium passivation. The toxicity of trivalentchromium is very low, and its performance is similar to hexavalent chromium, it isconsidered the most likely alternative technology. Using2024,6061and7075aluminumalloys as the test materials, it develops an environmentally friendly trivalent chromiumpassivator, and studies the performance of the film and its overcoatability with paint.This paper uses chromicsulfate as the main film-forming substances, the rare earthmetal salt as the auxiliary film-forming substances, through Single factor test andOrthogonal test, selecting the main ingredients and process conditions of chemicalconversion solution, finally the best formulations and process conditions of trivalentchromium passivation solution are as follows: chromicsulfate0.010mol/L, rare earthmetal salt0.020mol/L, complexing agent0.010mol/L, inhibitor0.025g/L, temperature30～35℃, time5min, pH value3.8～3.9.The passivation solution in accordance withthe above formulation is the green transparent liquid, the appearance of the conversionfilm is of uniform light blue.The trivalent chromium chemical conversion film has excellent performance,mainly in these areas: it can reach168h salt spray resistance, The corrosion resistance isfar superior to chrome-free passivation film of zirconium titanium class, the surface ofthe film is continuous complete and more dense than the passive film dealed withAlodine1200, electrochemical tests shows that the corrosion resistance of the trivalentchromium passivation film is equivalent to hexavalent chromium passivation film, theweight of the passivation film is about3～6mg/dm2in three kinds of aluminum alloys,within this scope of film weight, the passivation film has good adhesive force with paint,the trivalent chromium passivation film has little influence to the fatigue performance ofthe substrate, constrast to the passivation film prepared by Alodine1200, it shows that,the fatigue test results of two kinds of chemical conversion process are very close for2024aluminum alloy, for7075aluminum alloy, the fatigue strength of trivalent chromium passivation film is slightly above the passivation film of Alodine1200,between the two processes the difference of fatigue strength is about8.5%in themedium and long-life.After spraying aviation primer and topcoat in the surface of the conversion film, itshows that chemical conversion film has excellent matching capability with paint afterperformance tests about Adhesion, water resistance, oil resistance, salt spray resistanceand resistance to heat.更多还原