沸騰濃硫酸腐食によるぜい性材料の耐食性評価

概要

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The corrosion behaviors of ceramics(Si-SiC, Sic, Si_3N_4, Al_2O_3, ZrO_2)were examined in boiliing 95wt% sulfuric acid by measuring weight change, concentration of dissolved ions in the sulfuric acid, 4-point bending strength and apparent hardness calculated from Load-Depth curve obtained by Micro-Indentation technique. The corroded surface and the fracture surface of the specimens were analyzed by SEM and EPMA. The corrosion behaviors of these ceramics were divided into 3 types ; (1)Si-SiC and SiC showed excellent corrosion resistance because of protective oxide films which developed during immersion, (2)the bending strength, apparent hardness of Si_3N_4 and Al_2O_3 decreased with increasing immersion time because of corroded layers produced during immersion, and(3)the bending strength of ZrO_2 decreased with remarkable weight loss. The thickness(T)of oxide films and corroded layer produced on Si-SiC, SiC, Si_3N_4 and Al_2O_3 was evaluated from the depth(d)which was determined by the slope change on Depth-Lad/Depth curve. The relationship between T and d was described as T≈10d. The bending strengths of Si_3N_4 and Al_2O_3 were evaluated from thickness(T)of corroded layer and K_<Ic> obtained before immersion. As a result, the bending strengths of Si_3N_4 and Al_2O_3 could be determined with both the K_<Ic> and the cquivalent crack length(a_e)to 20d.
1999-07-15