engleski

PIXE Spectroscopy for Determination of Vapor Phase Corrosion Inhibitor Concentration

Anticorrosive polyolefinic films are being increasingly used in corrosion protection, for packaging of electronic products to protection of firearms of all sizes. The films are produced by coextrusion of polyolefine and organomolybdate-based vapour phase corrosion inhibitor. The goal of the described experiments was to determine how long do the films provide anticorrosive protection knowing only the approximate initial concentration range of 2 to 10% of organomolybdate salt and not knowing the lowest concentration needed to offer anticorrosive protection. The samples were used films of different age. The molybdate-based vapour phase corrosion inhibitor is supposed to slowly diffuse out of the film and form a protective layer on metal surface. Thereby its concentration in the film should decrease with time what also had to be confirmed. Because of very low concentration of molybdenum in the films the error of classical analytical methods would be greater than the expected concentration change or even concentration itself, to avoid it PIXE spectroscopy was applied. In PIXE (Particle Induced X-Ray Emission) spectroscopy the X-ray emission characteristic of a particular nuclei produced by ion beam impact on a material, is measured so it is possible to identify the nuclei and to determine its concentration in the sample if larger than 1 ppm. According to the concentration of molybdenum determined by PIXE and the age of the film, samples of different age were divided in three groups. One group of films showed no concentration change over time and had lowest concentration of molybdenum, below 4000 ppm. According to that, 4000 ppm was chosen as lowest protection limit. The other two groups of films had initial concentration about 6000 ppm and 8000 ppm that decreased at different rate to 4000 ppm in more than 6 years. To confirm that the concentration of molybdenum, i.e. vapour-phase corrosion inhibitor in polyolefinic film changed with time and the validity of division of samples into the groups, the films with highest concentration of molybdenum were kept in vacuum at 50&ordm ; ; C for 8 months and then the PIXE measurements were done again showing significant decrease in molybdenum concentration corresponding to age of a particular film.

PIXE spectroscopy; vapor phase corrosion inhibitor; anticorrosive film; DSC; FTIR; molybdate

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