三元青铜/环境界面上物质转移的化学行为

Chemical behavior of mass transfer at the bronze/environment interface

用模拟闭塞电池法(O.C.)研究了青铜在模拟环境介质0.028 mol·L-1NaCl+0.01 mol·L-1Na2SO4+0.016 mol·L-1NaHCO3中的局部腐蚀孔内或裂纹内的化学变化.通电32 h后闭塞区内溶液的pH值由7.00降至5.02,与此同时Cl-和SO42-向闭塞区内迁移,其浓集倍数分别是6.31和2.93;测定了闭塞区内外Cu、Sn、Pb金属离子的浓度,据此计算出溶解因子fSn/Cu小于1,fPb/Cu大于1,表明青铜中各元素选择性腐蚀的顺序为Pb>Cu>Sn,腐蚀速度Pb>Cu>Sn;用XRD分析了腐蚀产物的组成,解释了青铜文物表面腐蚀产物的分层现象,即从里到外为CuCl,CuCl和Cu2O,Cu的二价化合物.

A simulated occluded cell (O.C.) was used on the study of chemical changes in the local corrosion pits or crevices of archaeological bronze in simulated environment medium (0.028 mol&middotL-1 NaCl + 0.01 mol&middotL-1Na2SO4 + 0.016 mol&middotL-1 NaHCO3). It is found that the pH value decreases from 7.00 to 5.02 as anodic current passes the cell for 32 hours, meanwhile Cl- and SO42- migrate into the O.C. and their concentrate rate reaches 6.31 and 2.93, respectively. The metallic ion concentrations of Cu, Sn, and Pb in the O.C. and bulk solution were measured which were used to calculate the dissolution factors, fSn/Cu and fPb/Cu. The results of fSn/CuPb/Cu >1 indicate that the selective dissolution order and corrosion rates are Pb>Cu>Sn. The composition of corrosion products is analyzed and how the products are layered on bronze surface is explained. The corrosion products from inner to outer are CuCl, CuCl and Cu2O, cupric compounds respectively.