Hydrated chromium oxide (CrOX) layer on Tin Free Steel (TFS) is an extremely thin film, from about 50Å to 250Å in thickness. CrOX film thickness is an important factor for TFS to have corrosion-resistance and lacquer adhesion. An advanced on-line system for measuring thickness of CrOX film has been developed.
The main features of the instrument are as follows:
(1) Spectral reflectance mainly at ultraviolet wavelengths are measured, and the thickness is calculated from those multi-wavelength reflective curve.
(2) It has very simple structure, and consists of three main parts, that is, Hg-lamp, rotary filters, and integrating sphere with photomultiplier. Thus, it has good stability against various kinds of disturbances which occur at on-line measurement.
(3) Measurement is done nondestructively and continuously.
