Use of Infrared Specular Reflectance to Measure Chromate Coating Thickness and to Monitor the Chromate Conversion Process
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
A method for measuring the relative thickness of chromate coatings on reflective surfaces and for controlling the chromate conversion process is accomplished by using infrared specular reflectance. The measurement of the relative thickness then provides a means of inspecting the chromate coating for inter and intra lot variation and monitoring the chromate conversion process. A standard specular reflectance set up [*], used at an angle of 45Œ, obtains the spectra of the chromate coating on an aluminum surface as shown in Fig. 1. The strong peak at approximately 2090 cm-1 is due to a C X N stretch, and the natural logarithm of the integrated area under the 2090 cm-1 peak varies linearly with the time the aluminum surface is exposed to the chromate bath (Fig. 2).