Capacitance Loss Evolution of Zn–Al Metallized Film Capacitors Under Atmospheric Corrosion

Atmospheric corrosion is an important factor affecting the long-term reliability of metallized film capacitors (MFCs). Oxygen and moisture permeate into the MFC and initiate oxidation among layers, leading to the corrosion of electrodes, and thus contributing to the capacitance loss (CL). In this work, a CL- ${t}$ model is derived to study the capacitance characteristics of MFCs under atmospheric corrosion. Also, an accelerated aging test is carried out to provide data support for the model and investigate the effect of electrode composition on the anticorrosion ability. The results indicate that the CL is due to the surface roughness of polymer films, and for MFCs with certain aluminum content, the end corrosion is especially serious because of moisture permeation. The improvement in the resistance to atmospheric corrosion is found to be restricted as the aluminum level is high enough, which indicates that the aluminum content should be controlled within 10 wt%.