| In the production process of the fuel tank,resistance spot welding will damage the structure of the steel plate,which can easily lead to the occurrence of accidents such as gas leakage and explosion,This will bring great hidden danger for people's production and life.Therefore,it is very significance to research on the corrosion behavior and mechanism of the steel for car's fuel tank after resistance spot welding.This study uses inferior fuel oil was used as the corrosive environment?enterprise standard for inferior fuel:160PPm formic acid,120PPm acetic acid,and commercially available No.93 gasoline in accordance with a 1:1:1 configuration?,the base metals,heat-affected zone,and welding zone of galvanized,zinc-tin,and lead-steel after resistance spot welding were objects of the study,Chemical corrosion experiment was carried out,the experimental time was 1224 h and the temperature was 45?.The corrosion products morphology and the corrosion surface morphology were observed by SEM.The electrochemical experiments were carried out in 3.5%NaCl solution,the open circuit potential,polarization curve and AC impedance of each sample were tested at room temperature by using Ivium type classical electrochemical workstation.Through the above studies,the following conclusions were drawn:The results of electrochemical experiments show that the corrosion rates of the zinc,zinc-tin,and lead-steel in the base metals are the highest(1.981?A·cm-2?1.606 A·cm-2?1.835?A·cm-2),the corrosion rates in the weld zones are the smallest(1.271?A·cm-2?0.554?A·cm-2?1.263?A·cm-2);The corrosion rates of the galvanized steel welding zone,heat-affected zone,and base metal zone are the largest,and the corrosion rates of the corresponding three zones of the galvanized tin steel are the smallest,The lead-plated steel is between the two.The results of chemical corrosion experiments show that three kinds of steel weldments are mainly galvanic corrosion in the inferior fuel oil,the corrosion products of galvanized,zinc-tin,and lead steel weldments are mainly Zn?CH3COO?2·?H2O,Sn?CH3COO?2·?H2O,Pb?CH3COO?2·?H2O and Pb?OH?2.The annual average corrosion rates of the galvanized,zinc-tin,and lead-steel in the base metal areas are the largest?0.5723 mm/a?0.4250 mm/a?0.5127 mm/a?,the corrosion resistance is the worst,the annual average corrosion rates?0.1453 mm/a?0.0308 mm/a?0.1425 mm/a?in the weld zone is the smallest,and the corrosion resistance is the best;The annual average corrosion rates of the galvanized steel in the welding zone,heat-affected zone,and base metal zone are the largest,and the annual average corrosion rates of the corresponding three zones of the galvanized tin steel are the smallest,the lead-plated steel is between the two.In summary,combined with the analysis of chemical corrosion experiments and electrochemical experiments,the results show that in inferior fuel oil the corrosion resistance of the three steel welding zones is the best,and the corrosion resistance of the base metal zone is the worst;The corrosion resistance of the galvanized tin steel weldments is better than that of the lead-plated steel,lead-plated steel is slightly better than galvanized steel. |
PDF Full Text Request