Deterioration Process And Corrosion Detection Of Metal Packaging Materials

One disadvantage of metal packaging materials is that it is more likely to becorroded, but its corrosion mechanism and corrosion detection of metal cans stilltroubled the researchers. This paper focus on the deterioration process and corrosionmechanism of tinplate in functional drink and NaCl solution, the corroson detection ofbeverage cans.The corrosion process of a tinplate in functional beverage and NaCl solution wasinvestigated using electrochemical impedance spectroscope (EIS), scanning electronmicroscopy (SEM), energy dispersive X-ray spectroscopy (EDS), scanning probemicroscopy (SPM), and X-ray photoelectron spectroscopy (XPS), and a corrosionmechanism is proposed. The results show that the corrosion mechanism under twoconditons are different. We propose that the tinplate is mainly corroded by the organicacids that exist in functional beverages. X-ray photoelectron spectroscopy (XPS)results show that the corrosion product is mainly composed of a Sn(II)/Sn(IV) citratecomplex or an Fe(III) citrate complex. Furthermore, the corrosion product film is firstenriched with Sn and then enriched with Fe after immersion in functional beverage for24d. The corrosion of tinplate in0.5mol/L NaCl solution was mainly the dissolutionof carbon steel substrate because of the defects in the tin layer and the corrosionproduct was mainly γ-FeOOH.The anti-corrosion performance of lacquered-tinplate were evaluated usingimpedance modulus at low frequency and noise resistance, obtained from EIS and ENdata, respectively. Furthermore, the corrosion mechanism of lacquered-tinplate inenergy drink and NaCl solution was discussed. The results showed that the corrosionprocess could be divided into2stages: wetting of the organic coating and thecorrosion of the tinplate beneath the coating, and the wetting process was only acouple of days.The degradation coefficient is proposed to evaluate the degradation degree oforganic coatings by directly analyzing the Bode plots of the electrochemicalimpedance spectroscopy (EIS) data (1—100Hz). We investigated the degradation ofphenolic epoxy coating/tinplate system by EIS and the degradation coefficient value,which correlates well with the results of breakpoint frequency and variation of phase angle at10Hz. It is concluded that degradation coefficient can be used for the fastevaluation of degradation degree of organic coatings without constructingelectrochemical equivalent circuits in practical applications.An electrochemical sensor was designed to detect the corrosion degree of metalcans for beverage packaging, and the effective testing area of the sensor wasdetermined. Electrochemical impedance spectroscopy (EIS) and electrochemical noise(EN) were performed to detect the corrosion degree of beverage cans. ICP-MS resultsshowed that tin and iron release increased with storage time while EIS and EN resultsshowed that coating resistance, charge transfer resistance and noise resistancedecreased with the increase in storage time, thus indicating that the corrosion beneaththe organic coating induced a metal release. A clear and direct relationship wasobtained between ICP-MS and electrochemical data. The designed electrochemicalsensor was successfully applied to detect the performance of beverage cans andfurther provided scientific proof to evaluate the shelf life of metal cans for packaging.Chaos theory and the use of phase space reconstruction produce a novelmethodology to study electrochemical noise (EN) signals, obtaining novelinformation to distinguish corrosion types. To evaluate the chaotic nature ofelectrochemical noise, phase space is reconstructed and the embedding parameter isobtained by the mutual information and Cao’s methods. Subsequently, the correlationdimension is calculated. From the correlation dimension, we can conclude that localcorrosion shows a higher correlation dimension while passivation shows a lowercorrelation dimension.