Development and Corrosion Rate and Corrosion Mechanism of Dental Ag-Pd-Cu-Au alloys.

1.腐蚀速率（I_<corr>）使用以下等式获得; I_<corr>= K/Rp（K：恒定值）。采用6种Ag-Pd合金、4种Ag-Pd-Cu合金、1种Ag-Cu合金和4种市售牙科银基铸造合金作为试样，0. 1% HCl-Ringer溶液（pH=2）作为试验溶液。总之，<corr>与I/Rp成比例变化的I_的范围最小为2.3 × 10^<-8>，最大为4.4 × 10^<-5>（A/cm ^2），而K值则位于13.5 ~ 25.9 mV之间。平均K值为20 mV。因此，牙科用Ag基合金的Icorr可简单地由上述方程中的Rp代替20 mV的K来估算。结果表明，恒电量法可用于牙科合金腐蚀速率的快速测定。2.采用电化学技术、X射线光电子能谱表面分析和反射电子衍射研究了一种Ag-Pd-Cu-Ag合金在0.9%NaCl溶液中的腐蚀行为。在-100mV的负电位或损耗下，未观察到所测试的合金的腐蚀。在OmV ~+300mV电位范围内，合金表面氧化形成AgCl、AgO、Cu_2O、CuO、Cu（OH）Cl、CuO和CuCl_2等表面膜。合金中的Pd在+400mV和+500mV下被氧化成PdO_2。在+400mV和+500mV下阳极氧化的样品表面存在AgCl和Cu（OH）_2。AgCl的量大于Cu（OH）_2的量。

1. Corrosion rate (I_<corr>) is obtained using the following equation; I_<corr> = K/Rp (K:constant value). Six kinds of Ag-Pd alloys, four kinds of Ag-Pd-Cu alloys, one Ag-Cu alloy, and four kinds of commercial dental Ag-based casting alloys were used for the specimen and 0.1% H Cl ringer solution at pH=2, was used at the test solution in the study. In summary, I_<corr>, which changed in proportion to I/Rp, ranged from 2.3 x 10^<-8> at minimum and 4.4 x 10^<-5>(A/cm^2) at maximum, whereas the K values were localized between 13.5 and 25.9mV. The average K value was 20mV. Therefore, the Icorr of dental Ag-based alloys was estimated simply from the Rp substituting 20mV for K of the above equation. These findings revealed that the Coulostatic method is useful for rapid determination of the corrosion rate of dental alloys. 2. The corrosion behavior of a commercial Ag-Pd-Cu-Ag alloy in 0.9% NaCl solution was investigated by an electrochemical technique, surface analysis of X-ray photoelectron spectroscopy and reflection electron diffraction. No corrosion of the alloy examined was observed at negative potentials of -100mV or loss. In the potential region from OmV to +300mV, the alloy may be oxidized to form surface films of AgCl, AgO, Cu_2O, CuO, Cu(OH)Cl, CuO and CuCl_2 on the basis of the equilibrium potential for this system. Pd in the alloy was oxidized to form PdO_2 at +400mV and at +500mV. AgCl and Cu(OH)_2 were found on the sample surface anodized at +400mV and +500mV. The amount of AgCl was greater than that of Cu(OH)_2.