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Application of impendance methods for corrosion protecting properties of coated substrates in metal packaging

Anwendung von Impendanzmeßmethoden für Korrosionsschutzzeigenschaften von Beschichtungen im Bereich Metallverpackungen
: Hollaender, J.; Brandsch, R.

International meeting on Corrosion Science and Control Technologies '95. Proceedings
CONBRASCORR. Congresso Brasiliero de Corrosao <1995, Rio de Janeiro>
Conference Paper
Fraunhofer ILV ( IVV) ()
aluminium; Beschichtung; coating; impendance; Impendanz; Lack; lacquer; Metallverpackung; packaging; Stahl; steel

Electrochemical impedance spectroscopy (EIS) has enlarged the possibilities of material testing especially in practical applications within the field of metal packaging. Direct measurements on the surface of metal substrates by 2-pole EIS in combination with effective phase sensitive spectra fittings and parameter calculations are used to described type and properties of coatings. In the field of aluminium materials (foils and laminates) several examples are given for thin layer analysis (oxides, primers, adhesives,lacquers and plastic films) concerning thickness and topometric distribution of the coatings. Special attention is given to the analysis of layer combinations e.g. adhesives/films and the rapid testing methods concerning the delaminating and corrosive influence of several critical products packed. EIS applications in the sector of steel based packages are demonstrated on differnt substrates like passivated steel and tinplate, electrolytically coated chromium steel (ECCS) and non passivated tinplate from the same steel batch lacquered by an epoxiphenolic system. The influence of forming processes (cup drawing) on the creation of lacquer defects and areas of lower lacquer bonding is shown by EIS (AC/DC/AC-method). In addition the effect of thermal and hydrolytic stress during a sterilization process is worked out by EIS. Finally results are given from rapid assessments of lacquer stabilities towards packed stuffs and from pack test (food canning) trials, where the corrosive interaction and metal uptake during storage is correlated with the predictions of early EIS-measurements.