Electrochemical impedance spectroscopy (EIS) in the l00 kHz-10 mHz frequency range was employed as the main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl sol...Electrochemical impedance spectroscopy (EIS) in the l00 kHz-10 mHz frequency range was employed as the main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl solution. The EIS results obtained at the open-circuit corrosion potential have been interpreted using a model involving the impedance of particle to particle contact to account for the increasing resistance between zinc particles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical resistivity of the binder. Galvanic current and dc potential measurements allowed us to conclude that the cathodic protection effect of the paint takes some time to be achieved. The loss of cathodic protection is due to a double effect: the decrease of the Zn/Fe area ratio due to Zn corrosion and the loss of electric contact between Zn to Zn particles. Even when the cathodic protection effect by Zn dust become weak, the substrate steel is still protected against corrosion due to the barrier nature of the ZRP film reinforced by Zn.展开更多
Sphalerite in the Niujiaotang Cd rich zinc deposit, Duyun, Guizhou is characteristically light yellow in color with significant enrichment of cadmium which ranges from 0.83% to 1.97% (averaging 1.38%) in concentration...Sphalerite in the Niujiaotang Cd rich zinc deposit, Duyun, Guizhou is characteristically light yellow in color with significant enrichment of cadmium which ranges from 0.83% to 1.97% (averaging 1.38%) in concentration in the mineral, corresponding to an enrichment coefficient as high as 30.47 to 72.96. In comparison with other major Pb Zn deposits in the world (the Mississippi Valley deposits, and the Fankou and Jinding deposits in China) the Niujiaotang deposit is n-n×10 times richer in cadmium. Sphalerite in the deposit is also rich in Ga and Ge, but poor in In, Mn and Fe, suggesting some special mechanisms that govern the geochemical behavior of these trace elements. Except for a minor amount of independent minerals like greenockite, cadmium occurs mainly as isomorphous impurity in the crystal lattice of sphalerite. During weathering and leaching under supergene condition, cadmium was separated from Zn, resulting in some secondary minerals of Cd, including oxides and otavite.展开更多
Performance comparisons between organic and inorganic zinc rich paints (ZRPs) were carried out. Electrochemical impedance spectroscopy (EIS) measurements were used to assess the corrosion prevention performance of the...Performance comparisons between organic and inorganic zinc rich paints (ZRPs) were carried out. Electrochemical impedance spectroscopy (EIS) measurements were used to assess the corrosion prevention performance of the ZRP coatings. The results show that during the cathodic protection period the potentials of the epoxy systems are less negative than those of the silicate system. For the zinc rich ethyl silicate paints, the initial values of the resistance through the binder and the charge transfer resistance associated with zinc dissolution are several orders of magnitude lower than those of the organic zinc paints, while the initial values of the capacitance due to the binder layer between Zn dust and the double layer capacitance for zinc dissolution are several orders of magnitude higher than those of the organic zinc paints. Furthermore, the deterioration with time of capability of the zinc particles in the paint to provide cathodic protection to the steel was interpreted.展开更多
The influence of surface roughness on the performance of zinc rich paint(ZRP) coatings was studied. Electrochemical impedance spectroscopy(EIS) measurements were used to assess the corrosion prevention performance of ...The influence of surface roughness on the performance of zinc rich paint(ZRP) coatings was studied. Electrochemical impedance spectroscopy(EIS) measurements were used to assess the corrosion prevention performance of the ZRP coatings. Furthermore, the EIS data of the steel ZRP sea water system were interpreted according to equivalent circuit models and the corresponding parameters were derived to assess the coating deterioration with time. The results show that the rougher surface favors better protection effect of the ZRP coatings. The protection potential of ZRP coatings for the standards and codes of practice is -0.78 V(vs SCE).展开更多
文摘Electrochemical impedance spectroscopy (EIS) in the l00 kHz-10 mHz frequency range was employed as the main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl solution. The EIS results obtained at the open-circuit corrosion potential have been interpreted using a model involving the impedance of particle to particle contact to account for the increasing resistance between zinc particles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical resistivity of the binder. Galvanic current and dc potential measurements allowed us to conclude that the cathodic protection effect of the paint takes some time to be achieved. The loss of cathodic protection is due to a double effect: the decrease of the Zn/Fe area ratio due to Zn corrosion and the loss of electric contact between Zn to Zn particles. Even when the cathodic protection effect by Zn dust become weak, the substrate steel is still protected against corrosion due to the barrier nature of the ZRP film reinforced by Zn.
文摘Sphalerite in the Niujiaotang Cd rich zinc deposit, Duyun, Guizhou is characteristically light yellow in color with significant enrichment of cadmium which ranges from 0.83% to 1.97% (averaging 1.38%) in concentration in the mineral, corresponding to an enrichment coefficient as high as 30.47 to 72.96. In comparison with other major Pb Zn deposits in the world (the Mississippi Valley deposits, and the Fankou and Jinding deposits in China) the Niujiaotang deposit is n-n×10 times richer in cadmium. Sphalerite in the deposit is also rich in Ga and Ge, but poor in In, Mn and Fe, suggesting some special mechanisms that govern the geochemical behavior of these trace elements. Except for a minor amount of independent minerals like greenockite, cadmium occurs mainly as isomorphous impurity in the crystal lattice of sphalerite. During weathering and leaching under supergene condition, cadmium was separated from Zn, resulting in some secondary minerals of Cd, including oxides and otavite.
文摘Performance comparisons between organic and inorganic zinc rich paints (ZRPs) were carried out. Electrochemical impedance spectroscopy (EIS) measurements were used to assess the corrosion prevention performance of the ZRP coatings. The results show that during the cathodic protection period the potentials of the epoxy systems are less negative than those of the silicate system. For the zinc rich ethyl silicate paints, the initial values of the resistance through the binder and the charge transfer resistance associated with zinc dissolution are several orders of magnitude lower than those of the organic zinc paints, while the initial values of the capacitance due to the binder layer between Zn dust and the double layer capacitance for zinc dissolution are several orders of magnitude higher than those of the organic zinc paints. Furthermore, the deterioration with time of capability of the zinc particles in the paint to provide cathodic protection to the steel was interpreted.
文摘The influence of surface roughness on the performance of zinc rich paint(ZRP) coatings was studied. Electrochemical impedance spectroscopy(EIS) measurements were used to assess the corrosion prevention performance of the ZRP coatings. Furthermore, the EIS data of the steel ZRP sea water system were interpreted according to equivalent circuit models and the corresponding parameters were derived to assess the coating deterioration with time. The results show that the rougher surface favors better protection effect of the ZRP coatings. The protection potential of ZRP coatings for the standards and codes of practice is -0.78 V(vs SCE).
