tailieunhanh - Handbook Corrosion (1992) WW Part 3

Tham khảo tài liệu 'handbook corrosion (1992) ww part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Table 3 Planned interval corrosion test 3 Duplicate strips of low-carbon steel 19 X 75 mm or I X 3 in. were immersed in 200 mL of 10 AlCl3-90 SbCl3 mixture through which dried hydrogen chloride gas was slowly bubbled at atmospheric pressure. Temperature 90 C 195 F Value Interval days Weight loss mg Penetration Apparent corrosion rate Pm mils mm yr mils yr A1 0-1 1080 620 At 0-3 1430 270 At 1 0-4 1460 210 B 3-4 70 40 A2 calculated 3-4 30 18 A2 B A1 Conclusions Liquid markedly decreased in corrosiveness during the test and the formation of a partially protective scale on the steel was indicated that is metal became less corrodible. The causes for the changes in corrosion rate as a function of time are not given by the planned interval test criteria. The corrosivity of the liquid may decrease as a result of corrosion during the course of a test because of the reduction in concentration of the corrosive agent the depletion of a corrosive contaminant the formation of inhibiting products or other metal-catalyzed changes in the liquid. The corrosivity of the liquid may increase because of the formation of autocatalytic products the destruction of corrosion-inhibiting substances or other catalyzed changes in the liquid. Changes in the corrosiveness of the liquid may also arise from changes in composition that would occur under the test conditions even in the absence of metal. To determine if the latter effect occurs an identical test is run without test strips for the total time t. Test strips are then added and the test is continued for unit time interval. Comparison with A1 of corrosion damage from this test shows if the corrosive character of the liquid changes significantly in the absence of metal. The corrodibility of the metal in a test may decrease as a function of time because of the formation of protective scale or the removal of a less resistant surface layer of metal. Metal .