In order to shed light on the role of oxime additives as blocking agents of the cobalt-catalyzed autoxidative drying in alkyd paints, various techniques have been applied. Spectroscopic studies (Vis-NIR, 1 H NMR) of different model solutions show, together with investigations on the coordination chemistry of cobalt salts with oximes, that only weak interactions between cobalt and oximes can be evidenced; in several cases the residual water that is present is a stronger ligand than oximes for the cobalt ion. From CoCl 2 and methyl ethyl ketoxime (meko) the highly unstable complex [Co(meko)Cl 2 ] n has been isolated. The polymerization inhibition properties of different oximes were studied by TR-FTIR and SEC techniques. From EPR and GC-MS model experiments, it has been established that the free radicals formed in the coating compositon may readily add to the C=N double bond of the oxime, producing stable radical addition products that could inhibit further free radical chain reactions.

Paints and other coating systems form a solid layer during the film-forming process where different physical and chemical processes are important.Oxidative drying is a process in which the evaporation of solvents is followed by an oxidation process of the unsaturated binder under influence of oxygen in the air. This oxidative drying process is accelerated by the addition of catalysts, referred to as driers.

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