Research On Corrosion Behaviors Of Metal Cans For Beverage Packaging

Due to good leak tightness and long shelf life, metal packaging was widely used in beverage industries. But one disadvantage of metal packaging can is that it is more likely to be corroded. The corrosion of metal cans may lead food contaminated and food safety problem, which will threaten body and health of the human being. At present, the corrosion mechanism of metal tins is unclear. Therefore, for reducing the occurrence of food safety problem, it is more meaningful and reasonable to study the corrosion behavior and failure mechanism and predicate the corrosion life.First of all, the corrosion electrochemical behavior of tinplate used for raw materials of beverage cans in acidic solution is discussed. The results show that the corrosion current density value of tinplate was high, even reaches to 40μA/cm2 at early stage of immersion. In the middle stage of immersion, the matrix carbon steel was exposed and the main corrosion reaction was tin layer dissolved. At the last stage, corrosion rate of carbon steel was 14μA/cm2, which can be take short shelf life. Tin layer was completely dissolved after about one month.The galvanic corrosion trend between beverage can body tinplate and can bottom Al plate are investigated. The results show that difference value of galvanic potential is about 100mV and galvanic current is 16μA/cm2. The galvanic corrosion is tin dissolution primarily, which belongs to weak galvanic corrosion behavior so that the affection for shelf life of beverage container can be neglected.The research on the corrosion resistance of unpassivate and passivated tinplate used for acidic beverage can show that the tinplates used in our experiment are not efficient passivated. While the corrosion resistances, of four tinplates were improved significantly after using passivation method in this paper, especially, passivation effect of F1 tinplate was most obvious, indicating that the passivation method used in this paper is reasonable and effective. The results of the amount of tin show that, F3 tinplate was minimum amount of errors.The corrosion resistance of color printing iron immersion in acidic beverage solution shows that the coating resistance of color printing iron is much larger than 106Ω·cm2 after 11 months of immersion, indicating that epoxy phenolic resin on color printing iron still has protection ability. A good relationship between accelerated testing at low potential and natural immersion of color printing iron, meaning that accelerated testing at low potential can predict the corrosion resistance life of color printing iron.Secondly, based on a large number of beverage filled cans, the corrosion life prediction model of beverage cans with parameters of coating resistance and iron ion content is established by statistical analysis method. The gradual deterioration processes of beverages cans protection system are discussed using this model:the first stage is the rapid water penetration stage in coating; the second stage is the accumulation of infiltration and corrosion product. The meaning of model turning parameters Rc,tp and [Fe]tp are critical coating resistance and the critical concentration iron, respectively.As can be seen from the results of accelerated corrosion test of acidic beverage cans that, the trend of coating resistance of accelerated corrosion at low potential is consistent with that in natural immersion, indicating there is a good relationship between them. The accelerated method with low cathodic polarization could uses as a routine method with natural corrosion testing for predicating corrosion resistance life of metal beverage cans.