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Method to efficiently and accurately measure critical pitting temperature of stainless steel
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A technology for accurate determination of stainless steel, applied in the field of accurate determination of the critical pitting temperature of stainless steel, high efficiency, and evaluation of the pitting corrosion performance of stainless steel, which can solve the problems of inability to guarantee the same initial conditions of the sample, affecting the accuracy of the measurement results, and difficult temperature control. , to achieve the effect of shortening the experimental period, accurate pitting resistance, and convenient operation.
Inactive Publication Date: 2018-05-15
ANHUI UNIVERSITY OF TECHNOLOGY
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Problems solved by technology
Since the state of the sample changes continuously during the continuous measurement process, it is impossible to guarantee that the initial conditions of the sample at each temperature point are the same, and it is difficult to control the temperature during the continuous heating process. The solute ion concentration of the medium solution in the open container will vary with the water solvent The evaporation changes, which affect the accuracy of the measurement results
At the same time, the measurement cycle of the above methods is relatively long, time-consuming and laborious.
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Embodiment 1
[0031] Measure the critical pitting temperature of Fe20Cr9Ni cast duplex stainless steel.
[0032] Cut the sample line into 25mm×25mm×3mm sheet samples, remove oil stains, and polish the surface to 2000 # , to ensure that the wear marks of all samples are in the same direction, after cleaning with acetone and absolute ethanol, measure the surface area and weigh them after drying.
[0033] The configured medium solution (100g analytical pure FeCl 3 ·6H 2 O dissolved in 900ml 0.05mol / L hydrochloric acid solution) into a 400ml beaker, set the temperature values of different thermostats (water baths) (25-45°C, temperature interval 2.5°C, corresponding to figure 1 No. 1-8 in ), put the sample after the temperature of the medium solution is stable, such as figure 2 As shown, set the time and start the test.
[0034] After the test, the samples were taken out to clean up the corrosion products, dried and weighed, and the corrosion rates at different temperatures were obtained....
Embodiment 2
[0037] The critical pitting temperature of Fe20Cr9Ni cast duplex stainless steel aged at 750℃ was measured.
[0038] Cut the sample line into 25mm×25mm×3mm sheet samples, remove oil stains, and polish the surface to 2000 # , to ensure that the wear marks of all samples are in the same direction, after cleaning with acetone and absolute ethanol, measure the surface area and weigh them after drying.
[0039] The configured medium solution (100g analytical pure FeCl 3 ·6H 2 O dissolved in 900ml 0.05mol / L hydrochloric acid solution) into a 400ml beaker, set the temperature values of different thermostats (water baths) (20-40°C, temperature interval 2.5°C, corresponding to figure 1 No. 1-8 in ), put the sample after the temperature of the medium solution is stable, such as figure 2 As shown, set the time to start the test.
[0040] After the test, the samples were taken out to clean up the corrosion products, dried and weighed, and the corrosion rates at different temperatur...
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Abstract
The invention discloses a method to efficiently and accurately measure critical pitting temperature of stainless steel and belongs to the field of evaluation of metal local corrosion properties. A non-continuous synchronous measurement technique is used to control temperatures respectively for samples under same initial conditions through multiple thermostatic sets; different temperature values are set; a set temperature is maintained for a period of time; a medium solution container is sealed during test; after test, the samples are removed, cleaned and weighed; corrosion rates at different temperatures are calculated; therefore, critical pitting temperature of stainless steel is measured. The problem that the existing continuous single-sample measurement method has non-uniform initial conditions can be effectively solved; efficiency is greatly improved, and test cycle is greatly shortened. The method enables CPT (critical pitting temperature) value of stainless steel to be measured simply, efficiently and accurately so that pitting resistance of a material can be evaluated quickly and accurately, and effective means are provided for researches on pitting sensitivity of stainlesssteel; the method has important practical application value.
Description
technical field [0001] The invention belongs to the field of metal local corrosion performance evaluation, in particular to a method for evaluating the pitting corrosion performance of stainless steel, in particular to a chemical method for efficiently and accurately measuring the critical pitting temperature (CPT) of stainless steel. Background technique [0002] Pitting corrosion is a kind of hidden and destructive localized corrosion, which often occurs in easily passivated metals and alloys. Stainless steel exhibits good corrosion resistance due to the formation of a stable passivation film in many media, but in some media containing aggressive anions (such as Cl - , B - 、SCN - etc.) in the solution, the metalanodic dissolution in a small area often occurs and pitting or pitting occurs—pitting corrosion. The occurrence and development of pitting are related to many factors, among which the ambient temperature is an important aspect. As the temperature increases, the...
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