Study finds raindrops accelerate car corrosion

A team of materials scientists from the University of Cambridge has identified a previously underappreciated mechanism by which water can degrade a wide range of surfaces. Published in the journal *Advanced Materials* this week, the research demonstrates that even brief exposure to liquid water can trigger microscopic swelling in polymer‑based coatings, creating micro‑cracks that propagate under normal use. The investigators used high‑resolution microscopy and accelerated aging tests on common industrial substrates—including painted metal, ceramic tiles and composite polymers—to show that water molecules infiltrate the polymer matrix, disrupt intermolecular bonds, and induce a reversible expansion that, over repeated cycles, leads to irreversible structural failure.

The findings have immediate implications for sectors that rely on water‑resistant finishes, such as construction, automotive manufacturing and consumer electronics. Current protective standards focus primarily on preventing bulk water penetration, but the study suggests that surface moisture alone can initiate damage long before visible signs appear. Manufacturers are urged to reconsider coating formulations and testing protocols to address this capillary‑induced swelling effect. By highlighting a subtle yet pervasive source of wear, the research offers a pathway to more durable materials and could inform future guidelines for product longevity in humid environments.