Luminescent method for measuring the thickness of thin coating films on rough surfaces

Conclusions

A luminescent method has been developed for evaluating the thickness of thin transparent luminescent coatings on surfaces of solid bodies by means of an equipment consisting of instruments produced by our industry.

The high sensitivity of photomultipliers and the high definition of their luminous beam (of the order of 1μ ²) are suitable for measuring the surface of thin films either at separate points, or for plotting their thickness diagrams along a definite path of the tested surface.

This method can be recommended for evaluating oil coatings over rough metal surfaces. The method used for this purpose to date has consisted of applying lubricating layers of volatile solvents, with their thickness being evaluated by computation from the concentration of the solution and the area which it covered. This method contributes considerable errors. First, it is assumed that an oil film of a definite thickness is thus produced, whereas even on a smooth surface the oil is distributed nonuniformly, and all the more so on a rough surface. Second, the true area of a rough surface is not known, and it is assumed in calculations that the surface is smooth. These errors can be reduced by using the luminescent method.

The same technique can be used for evaluating the distribution of lubricants over a friction path, for testing the uniformity and continuity of certain decorative or insulating coatings, etc.

Thus, the measurement of film thicknesses by the luminescent method can be used both in scientific research and in industry.