Tham khảo tài liệu 'volume 05 - surface engineering part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 10 75 26 61 81 15 75 21 57 77 20 75 15 53 73 Source Aluminum Development Council a Anodic coating removed in chromic-phosphoric acid. Metallurgical factors have a significant influence on the effect of anodizing on reflectance. For minimum reduction reflectance the conversion of metal to oxide must be uniform in depth and composition. Particles of different compos do not react uniformly. They produce a nonuniform anodic coating and roughen the interface between the metal an oxide coating. Anodizing Conditions. The composition and operating conditions of the anodizing electrolyte also influence the lig reflectance and other properties of the polished surface. Figure 8 shows the effect of sulfuric acid concentre temperature of bath and current density on the specular reflectance of chemically brightened aluminum alloy data show that a particular level of specular reflectance can be produced by varying operating conditions. Fig. 8 Effect of anodizing conditions on specular reflectance of chemically brightened aluminum. Data are for a 5 pm mil anodic coating on 5457 alloy a 17 wt H2SO4. b wt H2SO4 Temperature of bath F Thermal Radiation. The reflectance of aluminum for infrared radiation also decreases with increasing thickness of anodic coating as shown in Fig. 9. These data indicate that the difference in purity of the aluminum is of mi significance. Figure 10 compares anodized aluminum surfaces and polished aluminum surfaces at 21 70 R V respect to absorptance when exposed to blackbody radiation from sources of different temperatures. Although anc aluminum is a better absorber of low-temperature radiation as-polished aluminum is a more effective absorbs blackbody radiation from sources at temperatures exceeding 3300 R 1850 K . Thickness of anodic film mils Fig. 9 Effect of anodic coating thickness on reflectance of infrared radiation. Temperature of infrared radiation source 900 C 1650 F . O Al. Al. Courtesy of Aluminum .
