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Ammonium Sulfate Corrosion heater device

imentalmacrographyandoriginalmacrography4.1 analysis of test results can be seen from the above results: ① is the chlorine corrosion products (Figure 2), indicating that the corrosion of the heater and the reaction solution related to the existence of a C1. ② heater tube inside the mouth showed pitting on the characteristics of the macro. Figure 1 shows that the nozzle does not occur outside of corrosion, pitting mainly concentrated in the tube inside the mouth. Figure 3 can also be seen near the weld corrosion corrosion significantly higher than other parts of the more serious cases. Comparing Figure 5a and Figure 5b, the specimen without sensitization does not appear on the corrosion characteristics of the macro, but on the surface appeared to be ammonium sulfate liquor pollution. Comparing Figure 6a and Figure 6b, after the specimen sensitized had more serious pitting. ③ can be seen from Figure 4, the specimen in the micro-pits on the show more, and some cracks appeared in the bottom of the pit. 4.2 Corrosion of austenitic stainless steel due to welding, the weld heat affected zone near the temperature of the sensitizing temperature range (generally believed that the 450 ~ 850 ℃), If you stay too long, will have a stainless steel sensitized E. Heater automatic welding process of welding, the welded structure is complex because the solution does not make the appropriate treatment process, and do not adopt the appropriate measures (such as local water, etc.) to reduce the material in the sensitizing temperature range of length of stay. Therefore, the nozzle heater near the weld heat affected zone sensitization took place. Can be seen from the test results, leading to sensitization of the weld near the heater in the nozzle of the important reasons of corrosion. The corrosion mechanism as follows: First,[link widoczny dla zalogowanych], since the temperature increases, the ability to increase the chromium carbide precipitation, carbon atoms to the grain boundary diffusion capacity than the grain boundary diffusion of chromium atoms to add the ability to increase quickly. So sensitized stainless steel will be produced in the grain boundary chromium depleted zone,[link widoczny dla zalogowanych], making the grain boundary of the passive film could deteriorate the integrity and compactness,[link widoczny dla zalogowanych], in a non-steady state; and chromium contents were made of stainless steel electrode potential drop, and so material The corrosion resistance decreased. * 200 * Second,[link widoczny dla zalogowanych], if the ammonium sulfate liquor in a high content of Cl, while the activity of anions (eg C1 a) of the destructive effects of passive film in the passive film is weak priority areas, such as the surface exposed to a grain boundary carbide objects or parts of sulfide inclusions, or defects in the passive film occurs at the local passive damage. Once the partial breakage of the membrane, stainless steel substrate exposed to the corrosive medium, the sensitized stainless steel grain boundary chromium depletion due to poor corrosion resistance, the occurrence of the initial solution, and then as a source of pitting corrosion pits [2]. Figure 1 and Figure 6 can be seen in the sample had pitting. Finally, when the liquid and the workpiece at a relatively high speed, uneven distribution of fluid pressure, the pressure changes in the larger case, the surface prone to cavitation [3]. Heater is in working condition this case, and because of the high-speed fluid flow, accompanied by erosion-corrosion of the produce. Figure la from the mouth of the heater inside the tube, Figure 3a of the hanging pieces can be seen signs of erosion-corrosion, and from these two diagrams can be seen in the vicinity of the weld (sensitized site) is significantly higher than other parts of the severe corrosion . In contrast sensitization experiment, the fluid flow is relatively slow, so the sample in Figure 6a can only see the phenomenon of pitting. 5 Conclusions and recommendations (1) heater in the processing of the welding process, welding position near to take effective measures are not leaving because of stainless steel for a long time in the sensitizing temperature range, and the reason is not due to structural welding and then make the appropriate solution processing, which makes stainless steel sensitization occurs, resulting in corrosion performance. (2) the erosion of the mother liquor of ammonium sulfate anion (C1 a) were higher, led to the sensitization of austenitic stainless steel parts produced pitting, while the relatively high speed of the conditions produced by cavitation and erosion-corrosion played a part in the acceleration of pitting corrosion. (3) after heating in the welding should be solution heat treatment, such as when for some reason can not be used in welding and other measures to reduce local water sensitized by the impact of the material. (4) The mother liquor of ammonium sulfate content of Cl one, so that a content of Cr to meet the requirements. Reference: Eli FENG Zhi Meng, Tsai Hong Fig. Austenitic stainless steel and clad plate processing and sensitizing temperature [J3. Petrochemical equipment, 2002,[link widoczny dla zalogowanych],31 (6) :38-39. E2] LIANG Cheng-hao and Foster. Sensitization of stainless steel to pitting corrosion of [J3. Corrosion Science and Protection Technology, 1996,8 (4) :281 - 285. E3] Wu Jian. Stainless steel, corrosion damage and corrosion technology (f) wear corrosion, cavitation corrosion and galvanic corrosion EJ]. Corrosion and Protection, 1998,19 (2) :39-4】.

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