Why does rainwater on new cars not dry easily?

[CooperFitz]

Rainwater on new cars does not dry easily because new cars often have a layer of anti-corrosion oil. Below is a related introduction to the waterproof rating of cars: Meaning: Taking IP54 as an example for the car waterproof rating index, IP refers to the protection safety level. The first digit after IP represents the solid-state protection level, and the second digit represents the liquid protection level. Current status: Currently, most electric vehicles in China can achieve a protection level of IP67, with some new energy models capable of reaching an actual wading height of 70mm. The maximum upper limit of wading ability can even approach a height of 1 meter.

[LeElaina]

As a seasoned driver with years of experience, I've noticed that rainwater dries slowly on new cars primarily because the fresh paint coating is too smooth and intact. The water doesn't spread out but instead forms small droplets, which evaporate slowly and cling tightly. This is especially true when parked in shady or high-humidity areas with poor air circulation, unlike my old car with its fine scratches and oxidized surface that allow water to disperse and evaporate quickly. New car owners should be careful not to use highly alkaline car wash detergents that could damage the coating, as this would affect its water-repellent properties. The car's color also plays a role—darker colors absorb heat faster and might dry slightly quicker, but it's still slow. The best solutions are to park in a sunny spot after rain or manually dry the car. Over time, as the paint ages, this phenomenon will lessen, but patience is key in the early stages.

[EmmettLee]

I just bought a new car two weeks ago, and after the rain stops, water droplets remain on the car body for a long time without drying. I feel the surface of the new car is too new and smooth, like glass, causing rainwater to form beads that don't flow and evaporate slowly, which is quite annoying. Normally, I park at the open-air company parking lot for my commute. When the humidity is low, it's okay, but when it's humid or parked under trees, the water stays even longer. I read some car forums saying that new cars have chemical coatings to reduce water absorption but also slow down evaporation, while older cars have rougher surfaces that spread water and heat up faster. To speed up drying, I now choose well-ventilated parking spots and sometimes bring a cloth to wipe the car lightly to avoid water stains. For maintenance, I make sure to wash the car regularly and gently to protect the new paint. This issue is something I'll gradually get used to—it's not a big deal.

[JohnFitz]

From a physical perspective, the slow drying of rainwater on new cars is attributed to the smooth and flawless surface coating, which causes water to form high-contact-angle beads with minimal surface area, resulting in insufficient heat transfer and slower evaporation. Specifically, the strong hydrophobicity of new paint keeps water droplets spherical and less prone to spreading, while evaporation relies on air flow and temperature; drying is further delayed in high-humidity environments or windless conditions. In contrast, oxidized surfaces of older cars with micro-defects facilitate water wetting and faster evaporation. As the coating wears with use, this phenomenon diminishes on new cars. Short-term solutions, such as optimizing parking locations, are straightforward and easy to understand based on scientific principles.

[SanLeonardo]

From a practical perspective, the slow drying of rainwater on a new car reminds me to focus on maintenance. The fresh coating causes water to linger and evaporate slowly, possibly due to the surface being too smooth for raindrops to bead up and dissipate heat. To address this, it's recommended to park in a ventilated area or under direct sunlight to speed up drying and prevent water stains from damaging the paint. When washing the car, use a neutral detergent to protect the coating. Regular waxing enhances protection but may prolong this characteristic; over time, with an older car, water beads will scatter and evaporate more quickly. Although rainwater retention seems minor, don't overlook it to avoid corrosion and costly repairs later. Get into the habit of carrying a soft cloth to wipe it down promptly.