Chemical vapor deposition (CVD) boride coatings obtained through thermal diffusion of boron into metallic base of engineering components provide significant improvement of wear and corrosion resistance, integrity and service life of the components in several times. Thermal diffusion process and coating quality are defined by the batch composition providing the boron deposition and diffusion, temperature and time of the process, type of metallic base and its surface quality, and engineering design of the CVD process system. The obtained coatings with thicknesses of 50-250 up to 300-400 mm (depending on the application) are uniform and dense with consistent "saw-tooth" structures (for carbon steels) through the entire surface of the components with no delamination issues. Wear test studies demonstrated the coatings' adequate performance defined by high hardness and specific morphology of the coatings.

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The purpose of this paper is to discuss the possible effect the type of petroleum thinner may have on the wet-edge time limit of one type of varnish. Similar performance may be expected of a pigmented varnish.Further work will center around other types of varnish and the corresponding pigmented varnishes.For the particular varnish tested here, the percentage of thinner remaining at the wet-edge time limit lay between 70 and 80 per cent.The viscosity of the varnish in the film at the wet-edge time limit was between rather narrow limits.A critical point was reached in the rate of change of viscosity shortly after the wet-edge time limit was reached. Beginning at this point the viscosity increased rapidly. The type and amount of kerosene must be considered in connection with the wet-edge time limit.The addition of a small amount of butanol to this varnish decreased the wet-edge time limit.Indications are that the type of kerosene used may affect the homogeneity of this particular varnish in a film at the wet-edge time limit.

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