Will the white primer exposed on a black car rust?
4 Answers
Black cars exposing white primer will not rust. Knowledge about car rust is as follows: 1. Introduction: Rust is a chemical reaction that occurs when iron is left for a long time. Iron is prone to rust, not only due to its active chemical properties but also largely related to external conditions. Moisture is one of the substances that make iron prone to rust. 2. Principle: Water alone will not cause iron to rust. Only when oxygen in the air dissolves in water, and the oxygen reacts with iron in a watery environment, does it produce a substance called iron oxide, which is rust. Rust is a reddish-brown substance, not as hard as iron, and easily flakes off. When a piece of iron completely rusts, its volume can expand up to 8 times. If rust is not removed, this spongy rust is particularly prone to absorbing moisture, causing the iron to deteriorate faster.
I've encountered similar situations before. When the black paint is scratched to reveal the white layer, it's usually the primer layer, which doesn't necessarily rust on its own because the primer is the first protective coating applied to the metal body, designed to prevent rust and corrosion. However, the issue is that it exposes the fact that the outer paint is damaged. If not addressed promptly, rainwater and moisture can seep into the underlying layers, gradually corroding the metal. I've had small scratches on my car that exposed the primer, and at first, it was fine, but after prolonged exposure to wind and sun, rust spots started to appear. Once rust spots form, they can spread, leading to higher repair costs. Try to avoid parking in damp places regularly, and washing and waxing your car periodically can delay the process. If the exposed area is small, you can use a touch-up pen yourself; for larger areas, it's better to visit a professional shop for a paint repair to avoid higher costs later. In short, prevention is key—don't let small issues turn into big problems.
From my experience, the primer itself doesn't rust—it's just a coating that shields against external elements. The real issue lies in the exposed spots: when rainwater and salt infiltrate, metal oxidation begins, leading to rust. Automotive primers are mostly rust-proof materials, commonly white in color, which doesn't mean the metal is exposed. You need to check the depth of the damage—light scratches that only reveal the primer might be fine, but deeper ones that reach the metal can be troublesome. I've seen many cases while repairing cars where owners ignored minor scratches, only to find their bumpers rusted through a year later. I recommend buying a touch-up pen for simple fixes or visiting a shop for professional repainting as soon as possible. Additionally, parking in dry areas can reduce risks, and regularly inspecting your car's paint condition can help prevent minor issues from escalating—make it a habit.
This issue really concerns me. When the black paint is scratched to reveal the white primer, if the metal layer isn’t further damaged, it’s naturally rust-resistant, acting like a barrier. But real-life conditions are unpredictable: car washes, rain, and dust buildup can eventually lead to corrosion starting on the metal. Last time my car got scratched and showed white spots, I observed for months without rust, but parking in humid areas can speed up deterioration. Safety first—don’t take risks by delaying. For small areas, try temporarily covering with tape to prevent spreading. A budget-friendly option is to buy a touch-up kit for DIY repair; for a professional fix, go for repainting. The key is to act fast—don’t treat it as trivial.
