Measurement of dielectric constant of paint coated aluminium panel through microwave non destructive testing at frequency 18 to 26GHz (K Band) / Bibi Nawsheen Ebrahim Saib

Microwave non-destructive testing of paint and primer in components commonly used in moist and salty environment are very crucial in the investigation of signs of corrosion. In this paper, we present a method for measuring the dielectric properties and loss factor of paint coated aluminium panels using the metal-backed method. Complex reflection coefficient (Sn) is measured for Plexiglas container backed by metal plate. Dielectric constant and loss factor were measured for corrode and non-corrode paint coated aluminium panel in the frequency range of 18 to 26GHz (K-Band). The thru, reflect and line (TRL) calibration technique were used to eliminate the effect of undesirable multiple reflections. The dielectric constant for corrode paint coated aluminium panels is 2.9± 0.1 and for non-corrode paint coated aluminium panel is 2.5±0.1, showing that the dielectric constant of corrode samples are higher than non-corrode ones. The loss factor for corrode aluminium panels is ranged from -0.02 to -0.01 and for non-corrode aluminium panels, the loss factor is from -0.083 to -0.008. Loss factor for corrode aluminium panel is higher than that of non-corrode aluminium panel. The differences could be due to errors in the magnitude and phase of Su , surface of the paint coated aluminium panel and the air-gap effect during the assembly of the sample.