Rubber-Induced Corrosion of Painted Automotive Steel: Inconspicuous Case of Galvanic Corrosion

Rubber components filled with carbon black are widely used in vehicles for sealing, preventing water ingress, and reducing vibration and aerodynamic noise. However, carbon particles increase the electrical conductivity of rubber. When a carbon-filled rubber part comes into contact with the metal car body, it may act as a cathode, accelerating metal corrosion via galvanic coupling. This study combined volume resistivity and zero-resistance ammeter (ZRA) measurements, resistometric corrosion monitoring, and accelerated corrosion testing to assess the effect of rubber conductivity on the corrosion degradation of painted car body panels in defects. More conductive rubber induced a higher galvanic current and accelerated paint delamination from defects. Real-time monitoring confirmed an earlier onset of corrosion and higher corrosion rates for steel coupled with conductive rubber. These findings emphasize the importance of using low-conductive rubber with resistivity from 104 Ω·m to minimize the risk of galvanic corrosion of the car body.