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

1.腐蚀速率(I_&lt；Corr&gt；)由下列公式得到：I_&lt；Corr&gt；=K/Rp(K为常量)。用6种银-钯合金、4种银-钯-铜合金、1种银-铜合金和4种商品银基铸造合金作为试件，在pH=2的条件下，用0.1%的氯化氢林格液作为试液。综上所述，I_&lt；corr&gt；与I/Rp成正比变化，最小为2.3×10；-8&gt；，最大为4.4×10；-5&gt；(A/cm2)，而K值集中在13.5-25.9 mV之间。平均K值为20 mV。因此，用20 mV的Rp代替上述公式中的K，可以简单地估算出牙科银基合金的Icorr。这些结果表明，恒压电位法是快速测定牙科合金腐蚀速度的有效方法。2.用电化学方法、X射线光电子能谱表面分析和反射电子衍射法研究了一种商用Ag-Pd-Cu-Ag合金在0.9%NaC l溶液中的腐蚀行为。在负电位为-100 mV或损耗时，未观察到合金的腐蚀。在OMV~+300 mV的电势范围内，根据该体系的平衡电势，合金可被氧化生成AgCl、AgO、Cu2O、CuO、Cu(OH)Cl、CuO和CuCl2的表面膜。合金中的Pd在+400 mV和+500 mV下氧化生成PdO_2。在+400 mV和+500 mV的阳极氧化后，样品表面有AgCl和Cu(OH)2生成。氯化银的量大于氢氧化铜的量。

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.