三元青铜/环境界面上物质转移的化学行为

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SO24-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.

Chemical behavior of mass transfer at the bronze/environment interface

A simulated occluded cell (O.C.) was used on the studyof chemical changes in the local corrosion pits or crevices ofarchaeological bronze in simulated environment medium(0.028 mol$cdot$L$^{-1}$ NaCl + 0.01 mol$cdot$L$^{-1}$Na$_{2}$SO$_{4}$ + 0.016 mol$cdot$L$^{-1}$ NaHCO$_{3}$). It isfound that the pH value decreases from 7.00 to 5.02 as anodiccurrent passes the cell for 32 hours, meanwhile Cl$^{-}$ and SO$^{2-}_{4}$migrate into the O.C. and their concentrate rate reachs 6.31 and2.93, respectively. The metallic ion concentrations of Cu, Sn, andPb in the O.C. and bulk solution were measured which were used tocalculate the dissolution factors, $f_{rm Sn/Cu}$ and $f_{rm Pb/Cu}$.The results of $f_{rm Sn/Cu}<$1 and $f_{rm Pb/Cu}>$1 indicate that theselective dissolution order and corrosion rates are Pb$>$Cu$>$Sn. Thecomposition of corrosion products was analyzed and how the products arelayered on bronze surface is explained. The corrosion products from innerto outer are CuCl, CuCl and Cu$_{2}$O, cupric compounds respectively.