APPLICATION OF METHODS FOR DETERMINATION OF THE VOLATILE CORROSION INHIBITORS CONTENT IN COMBINED PACKAGING MATERIALS

Abstract

One of the modern means of corrosion protection of metal products during transportation and storage is packaging materials containing volatile corrosion inhibitors. The efficiency of the metal protection is highly dependent on their content in the packaging materials. Present study considers the peculiarities of practical application of Synchronous Thermal Analysis method and Walki Wisa (Finland) method for determination of the corrosion inhibitor content in packaging combinations. The packaging materials used in the study were the crepe paper laminated with thermoplastic polymer on one side, onto which the water solutions of inhibitors Koring 501, 505 (Cortec, USA) and UNI (a mixture of sodium nitrite and urotropine in relation 1:1, Russia) containing 5 % (mas.) of active substance were applied with a roller. After application of the solution the paper was subjected to drying at 80 °C for 35 min. The residual content of inhibitors was determined by two methods: thermogravimetric analysis using STA 449 F3 Jupiter and the method of washout according to the Walki Wisa method. It was shown that washout method requires preliminary isolation of inhibitor from packing material in the form of its aqueous extract. It was found that the inhibitor content indices obtained by the washout method have higher values compared to the initial samples which is probably caused by the water extraction of other components from combined material together with the inhibitor. The content of the inhibitor in the materials under study and the temperature of the maximum rate of inhibitor volatilization were determined by the thermogravimetric analysis. The sample with UNI inhibitor had the highest inhibitor content (13 %) and a higher maximum volatilization temperature compared to the other samples. This may be due to the overlapping processes of urotropin removal and cellulose fibers decomposition. The method of thermogravimetric analysis can be applied for determination of the inhibitors removing up to 200 °C. It is noted that both considered methods have certain limitations and can be used for approximate determination of the inhibitor content in paper-based composite packaging materials.