There are significant differences between laboratory tests and field tests when selecting corrosion-resistant materials
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This post was last edited by Wang Wei2 on 2023-12-21 at 09:37. There are significant differences between laboratory tests and field tests when selecting corrosion-resistant materials. When selecting such materials based on the process media and conditions, these differences between laboratory and field tests are considerable, so special attention must be paid to them. As shown in the example below: In a pilot plant, an industrial organic synthesis experiment is carried out; the excess acid is partially neutralized with ammonia, the slurry is filtered, and the ammonium bisulfate filtrate is sent to a second unit where it is ultimately converted into sulfuric acid an. Past experience and tests on (equipment components of the sulfuric acid AN plant) show that 316 stainless steel is highly corrosion-resistant for the entire process. However, two-stage tests were conducted for safety: from acid to bisulfate, and from bisulfate to sulfate. Tests conducted by preparing solutions using laboratory chemicals showed that 316 stainless steel possesses excellent corrosion resistance. However, actual pilot-scale solutions yield different results; even slightly heated solutions (around 35°C) cause rapid corrosion of the stainless steel surface, leading to a degradation of the metal structure. The reason is that the partially neutralized acids contain about 1% of partially decomposed residual organic matter, which severely damages the passivation film of stainless steel in less than 4 hours. Note that this example shows that the design of material selection tests should simulate the actual operating conditions of the equipment as closely as possible; therefore, the environmental conditions must be determined in advance, especially with regard to any minor impurities present in the environment.
When selecting corrosion-resistant materials, there are significant differences between laboratory tests and field tests. Chemical tests under laboratory conditions may not be sufficient to simulate the specific conditions in actual applications. For example, in the case mentioned above, 316 stainless steel demonstrated excellent corrosion resistance in solutions prepared with laboratory chemicals; however, during actual pilot tests, the small amount of organic substances present in the solution severely damaged the passivation film, leading to rapid corrosion of the stainless steel. This indicates that during material selection tests, the experiments designed should simulate real-world usage conditions as closely as possible, with particular attention paid to the level of impurities in the environment; only in this way can the corrosion resistance of the materials be assessed more accurately. .