engleski

Spectroscopic Determination of Vapor Phase Corrosion Inhibitor Concentration in Anticorrosion films

Anticorrosion films, produced by coextrusion of polymer and vapour phase corrosion inhibitor (VCI) that provides protection by migrating out of the film and forming a layer on a metallic surface covered by it, are being increasingly used in corrosion protection. This investigation had several goals: - to identify the polymer carrier and the VCI of a particular set of anticorrosion films, - to confirm migration of VCI and determine how long the films provide protection, - since the VCI was identified as an organomolybdate salt, to determine its concentration using UV-VIS spectroscopy. The polymer carriers of analysed films of various ages were identified as LD-polyethylene. Particle induced X-Ray emission (PIXE) spectroscopy showed that the films contained significant amounts of molybdenum implying the VCI was molybdate-based. Based on the concentration of molybdenum and the age of the film, the samples were divided into three groups. One group had almost constant concentration of molybdenum below 4000 ppm, accordingly 4000 ppm was chosen as lowest concentration offering protection. The other two groups of films had initial concentration of Mo about 6000 ppm and about 8000 ppm that decreased at different rate to reach 4000 ppm in more than 6 years. To confirm the migration of the VCI and the validity of division of samples into the groups, the selected films were kept in vacuum at 50º C for 8 months and then the PIXE measurements were repeated showing significant decrease in Mo concentration corresponding to age of a particular film, the differences between the groups remained. The UV-VIS spectra of the anticorrosion films were recorded showing two prominent absorptions at about 710 and 610 nm. The intensities of absopritons at 710 nm had excellent correlation to molybdenum concentrations determined by PIXE so UV-VIS spectroscopy could be used to control the decrease of VCI concentration.

R spectroscopy; DSC; diffusion; molybdate; LDPE

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