In recent decades, the demand for cold-rolled steel sheets has remarkably increased. To prevent the sheets from rusting before the manufacturing process, a layer of rust-preventive oil has to be coated on the sheets. ...In recent decades, the demand for cold-rolled steel sheets has remarkably increased. To prevent the sheets from rusting before the manufacturing process, a layer of rust-preventive oil has to be coated on the sheets. In this study, the shipment and storage environments were simulated through a salt spray test and a damp-heat experiment, respectively, and the packaging status of the sheets was imitated by a laminated sheet test. The protection effect of oil on the steel sheet was investigated under the different environmental conditions and oil weights by using electrochemical approaches, scanning electron microscopy （ SEM）, and X-ray diffraction （XRD） techniques. It was found that chloride ions had more severe effects on the corrosion resistance of the oils than hydrothermal conditions did. This was shown in the sheets with oil weights of 0.4,0.9 ,and 1.2 g · m^-2 ,which were too severely corroded after a four-hour salt spraying test to meet the demands of subsequent processing. However, the sheets showed satisfactory corrosion resistance after a three-week damp-heat experiment with a temperature of 49 ℃ and 95 % RH. In addition, it was disclosed that the penetration of the chloride ions determined the protection mechanism of the oil, i. e.,the corrosion resistance was initially enhanced by the increase in the oil content. As long as the chloride ion reached the interface between the oil film and the sheet, the oil distribution became the predominant factor in the protection of the sheet. The corrosion mechanism of the steel sheet was dependent on the stacking style of the sample. When exposed to air, the corrosion product of the sample was rust red with a composition of Fe2O3, whereas the black product that is mainly composed of Fe3O4 was found on the edge of the laminated sheets, which resulted from the oxygen concentration cell.展开更多
Potential’s fluctuation of rust preventing oil film during its degradation was studied using wirebeam electrode. Being non-destructive and simple, potential measurement is a very repetitive method. Otherelectrochemic...Potential’s fluctuation of rust preventing oil film during its degradation was studied using wirebeam electrode. Being non-destructive and simple, potential measurement is a very repetitive method. Otherelectrochemical testing method, e. g., polarization resistance, can breakdown the integrity of oil coating byDC current; EIS is time consuming. As a special electrochemical sensor, wire beam electrode contains 101wires of mild steel wires, and it is helpful to improve the reproducibility of electrochemical test evidently.Using this electrode, the electrochemical parameters and their distribution which was related to under filmcorrosion process are measured directly so as to describe potential’s fluctuation of rust preventing oil film. Itis pointed out that there is potential’s fluctuation on rust preventing oil film during its degradation, and thischaracteristic has direct effect on the self-repairing ability of rust preventing oil film. However, for the uncoated metal electrode and base oil film, there is no such behavior. It is also pointed out that inhibitors in theoil film have direct effect on its self-repairing ability.展开更多
文摘In recent decades, the demand for cold-rolled steel sheets has remarkably increased. To prevent the sheets from rusting before the manufacturing process, a layer of rust-preventive oil has to be coated on the sheets. In this study, the shipment and storage environments were simulated through a salt spray test and a damp-heat experiment, respectively, and the packaging status of the sheets was imitated by a laminated sheet test. The protection effect of oil on the steel sheet was investigated under the different environmental conditions and oil weights by using electrochemical approaches, scanning electron microscopy （ SEM）, and X-ray diffraction （XRD） techniques. It was found that chloride ions had more severe effects on the corrosion resistance of the oils than hydrothermal conditions did. This was shown in the sheets with oil weights of 0.4,0.9 ,and 1.2 g · m^-2 ,which were too severely corroded after a four-hour salt spraying test to meet the demands of subsequent processing. However, the sheets showed satisfactory corrosion resistance after a three-week damp-heat experiment with a temperature of 49 ℃ and 95 % RH. In addition, it was disclosed that the penetration of the chloride ions determined the protection mechanism of the oil, i. e.,the corrosion resistance was initially enhanced by the increase in the oil content. As long as the chloride ion reached the interface between the oil film and the sheet, the oil distribution became the predominant factor in the protection of the sheet. The corrosion mechanism of the steel sheet was dependent on the stacking style of the sample. When exposed to air, the corrosion product of the sample was rust red with a composition of Fe2O3, whereas the black product that is mainly composed of Fe3O4 was found on the edge of the laminated sheets, which resulted from the oxygen concentration cell.
文摘Potential’s fluctuation of rust preventing oil film during its degradation was studied using wirebeam electrode. Being non-destructive and simple, potential measurement is a very repetitive method. Otherelectrochemical testing method, e. g., polarization resistance, can breakdown the integrity of oil coating byDC current; EIS is time consuming. As a special electrochemical sensor, wire beam electrode contains 101wires of mild steel wires, and it is helpful to improve the reproducibility of electrochemical test evidently.Using this electrode, the electrochemical parameters and their distribution which was related to under filmcorrosion process are measured directly so as to describe potential’s fluctuation of rust preventing oil film. Itis pointed out that there is potential’s fluctuation on rust preventing oil film during its degradation, and thischaracteristic has direct effect on the self-repairing ability of rust preventing oil film. However, for the uncoated metal electrode and base oil film, there is no such behavior. It is also pointed out that inhibitors in theoil film have direct effect on its self-repairing ability.
