We have investigated influence of concentrations of LiOH and Li 2 MoO 4 on corrosion behavior of SS400 carbon steel immersed in concentrated LiBr solutions at 393 and 438 K for a short period about 0.2 ks. The corrosion behavior was evaluated by measurement of polarization curve. As a result, the following were obtained: Addition of LiOH to 65 mass% LiBr solution induced suppression of cathodic current around the corrosion potential to shift the corrosion potential lower. Further, two-step active dissolution current was found around the corrosion potential and passive current in the higher potential region. On the other hand, addition of 0.03 mass% Li 2 MoO 4 to 65 mass% LiBr + 0.2 mass% LiOH solution induced small suppression of cathodic current around corrosion potential, and more addition of 0.06 mass% made the cathodic current slightly increase. Two-step active dissolution and passivation phenomena were found in the anodic polarization curve like those in the solution without Li 2 MoO 4 . The anodic current density was almost independent of the concentration of Li 2 MoO 4 . Corrosion rates of the steel immersed in various solutions at 393 K for the short period were almost the same as 1.5 A m 2 . In the solutions at 438 K, corrosion rate decreased with an increase in LiOH concentration and increased with an increase in Li 2 MoO 4 concentration.
A simple test method is proposed for reproducing stress corrosion cracking of pure copper in ammoniacal environment. A test tube of ammonia aqueous solution and C-ring specimens sampled from a pure copper tube were put in a 500mL polypropylene bottle for three weeks under room temperature. The pure copper tubes used in this work were high phosphorous deoxidized copper tube containing 0.028% P, low phosphorous deoxidized copper tube containing 0.007% P and oxygen-free copper tube without P. Tempers of these tubes were H, 1/2H and O defined in JIS H0500. Intergranular corrosion or intergranular cracking was occurred on the sur face of P-deoxidized 1/2H and O copper tubes under gas-phase ammonia derived from 1 to 9% ammonia water, while intergranular corrosion was not observed in the oxygen-free copper and all H-tempered copper tubes. It was found that no stress corrosion cracking occurs in the pure copper tubes without phosphorous or with small crystal grains by work hardening.
We have tried to measure polarization curves of SS400 carbon steel in concentrated LiBr solutions over 393 K, and investigated the influence of temperature as well as concentrations of LiOH and Li 2 MoO 4 on its corrosion behavior. Test solutions were 65 mass% (mass% is replaced by % hereafter) LiBr solutions containing 0 to 0.2% LiOH and 0 to 0.03% Li 2 MoO 4 . Test temperatures were 393 and 438 K. The test solutions were deaerated. The specimen was immersed in the test solution for a short time of 0.3 ks and was subjected to measurement of polarization curve in the same solution. As a result, the followings were obtained: The anodic current density in 65% LiBr solution without LiOH increased monotonically with a rise in a potential, and the relation was maintained regardless of Li 2 MoO 4 addition and temperature change. In 65% LiBr solutions with LiOH up to 0.2% at 393 and 438 K, the anodic polarization curves showed active dissolution and passivation. When 0.05% LiOH was added to the 65% LiBr solution, the corrosion potential negatively shifted, and the potential was maintained regardless of more addition of LiOH. As a LiOH concentration increased, a pitting potential was raised. The polarization curves at 393 and 438 K showed almost no change regardless of addition of 0.03% Li 2 MoO 4 , meaning that Li 2 MoO 4 had almost no effect on corrosion inhibition to the specimen for the short immersion. The corrosion rate at 393 K was approximately 0.3 A•m ¹2 regardless of the addition of LiOH nor Li 2 MoO 4 . Whereas, the corrosion rate at 438 K slightly decreased with increasing LiOH concentration, regardless of the addition of Li 2 MoO 4 . Cathodic current density in the solution with 0.2% LiOH and 0.03% Li 2 MoO 4 increased with a rise in a temperature on the basis of Arrhenius relation. It is thought that insufficient effect of LiOH and Li 2 MoO 4 on corrosion inhibition was observed because of a short immersion time of 0.3 ks before measurement of polarization curves.
This research aimed to investigate transients of corrosion morphology and weight loss of Cu in concentrated LiBr aqueous solution for understanding corrosion process of copper parts in an absorption heat pump. Cu plate specimens were immersed in an aqueous solution containing 65 mass% LiBr and 0.2 mass% LiOH at 353 K for various times, and then subjected to weight measurement tests and surface analysises. The specimen immersed in the solution suffered pit-like corrosion. The number of the pit increased linearly with an increase in an immersion time until 691.2 ks, and thereafter almost no pit was initiated. Each pit was semi-spheroid, and grew at a constant rate in each direction of horizontal and vertical. A corrosion weight loss showed an accelerated increase as an immersion time elapsed. The transients of the weight loss until 1728 ks was successfully simulated by assuming the corrosion process of the initiation and the growth of the pits. The simulation also revealed that a corrosion area was in good agreement with the whole specimen surface in around 1728 ks, and then that aspect of the corrosion shifted from pit-like corrosion to general corrosion. The empirical corrosion rate after 1728 ks obtained by the weight measurement test was also in good agreement with the vertical growth rate of the pit.
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