• 한국표면공학회지
• /
• 제38권6호
• /
• pp.241-247
• /
• 2005

Effects of Al and Cr alloying elements on the corrosion behavior of Fe-Al-Cr alloy system was investigated using potentiodynamic and cyclic potentiodynamic polarization tests(CPPT) in the $H_2SO_4$ and HCI solutions. The corrosion morphologies in Fe-Al-Cr alloy were analysed by utilizing scanning electron microscopy(SEM) and EDX. It was found that the corrosion potential of Fe-20Cr-20Al was highest whereas the critical anodic current density and passive current density were lower than that of the other alloys in 0.1 M $H_2SO_4$ solution. The second anodic peak at 1000 mV disappeared in the case of alloys containing high Al and low Cr contents. Pitting potential increased with increasing Cr content and repassivation potential decreased with decreasing Al content in 0.1 M HCI solution. Fe-Al-Cr alloy containing high Al and Cr contents showed remarkably improved pitting resistance against $Cl^-$ attack from pit morphologies.

• 한국표면공학회지
• /
• 제37권6호
• /
• pp.350-359
• /
• 2004

Stress corrosion cracking(SCC) characteristics of shot-peened stainless steel containing Ti (0.09 wt%-0.92 wt%) fabricated by the vacuum furnace were investigated using SCC tester and potentiostat. The homogenization and the sensitization treatment were carried out at $1050^{\circ}C$ for 1hr and $650^{\circ}C$ for 5 hr. The samples for SCC were shot-peened using $\Phi$0.6 mm steel ball for 4 min and 10 min. Intergranular and pitting corrosion characteristics were investigated by using EPR and CPPT. SCC test was carried out at the condition of$ 288^{\circ}C$, 90 kgf pressure, water with 8 ppm dissolved oxygen, and $8.3xl0^{-7}$/s strain rate. After the corrosion and see test, the surface of the tested specimen was observed by the optical microscope, TEM and SEM. Specimen with Ti/C ratio of 6.14 showed high tensile strength at the sensitization treatment. The tensile strength decreased with the increase of the Ti/C ratio. Pitting and intergranular corrosion resistance increased with the increase of Ti/C ratio. Stress corrosion cracking strength of shot-peened specimen was higher than that of non shot- peened specimen. Stress corrosion cracking strength decreased with the increase of the Ti/C ratio.

• 대한치과보철학회지
• /
• 제37권5호
• /
• pp.672-686
• /
• 1999

The purpose of this study was to compare the casting problem and corrosion behavior in two types of HL Hexed abutments of the Steri-Oss system ; gold/plastic coping and gold coping. The anodic Polarization behavior, the galvanic corrosion between abutments and Type III gold alloys, before and after casting were analyzed, and the crevice corrosion of casting samples was analyzed with the CPPT test and the SEM. The results are as follows : 1. Anodic polarization behavior of samples ; Before casting, gold/plastic coping and gold coping was shown to have a similar corrosion pat-terns. Type III casting gold alloy was shown to have a lower corrosion potential and passivation film. Corrosion potential of the case of gold/plastic coping after casting was higher than that of gold coping, but the region of passivation film for gold/plastic coping was smaller than that of gold coping. 2. Galvanic corrosion behavior of samples ; Contact current density between casting gold alloys and gold/plastic before casting was higher than that between gold coping and casting gold alloy Galvanic corrosion of samples after casting was shown to have similar contact current density 3. Crevice corrosion behavior of samples ; Crevice corrosion resistance of casting sample using gold coping was lower than that of cast-ing sample using gold/plastic coping, and a severe corrosion pattern was observed at the abutment-casting gold alloy interface by the SEM.