What Does Exposed Primer Look Like?

[StHazel]

When you run your finger over a scratch and feel obvious unevenness or roughness, it means the primer has been exposed. Below is relevant information: The Function of Automotive Primer: Automotive primer is the first layer of paint directly applied to the surface-treated metal parts, forming the foundation of the entire coating system. It is designed to have excellent adhesion to the substrate, good compatibility with intermediate or top coats, and must provide superior corrosion resistance, rust prevention, oil resistance, chemical resistance, and water resistance. Requirements for Automotive Primer: Depending on its application area on the vehicle, automotive primer must exhibit strong adhesion to the substrate, compatibility with subsequent intermediate or top coats, and possess excellent corrosion resistance, rust prevention, oil resistance, chemical resistance, and water resistance. Additionally, the primer film must meet mechanical performance standards such as appropriate hardness, gloss, flexibility, and stone chip resistance.

[Braxton]

A few days ago I noticed several scratches on the car body where the color was noticeably different from the surrounding area. For example, on the dark blue paint, the exposed underlying layer appears white with no gloss at all, and feels rough to the touch. After rain and washing the car, I noticed that the areas around the scratches started to turn yellow and rust, with a slightly raised texture when touched. This situation definitely indicates that the primer has been exposed, because normal paint scratches usually just turn white or show color variations that can be resolved with polishing. However, when the primer is exposed, the entire color layers separate, much like when new black paint reveals grayish-white primer at the edges, which is particularly conspicuous. If not addressed promptly, rainwater can corrode the metal panel, leading to widespread rust that even touch-up paint can't fix. I recommend not delaying in such cases—use a touch-up pen to temporarily cover and prevent rust, and seek professional repair as soon as possible for the safest solution.

[LaIsaac]

The most obvious sign of exposed primer is a sudden color change at the scratch. Last time my car was parked by the roadside, it got scraped by an electric scooter, leaving a 7-8 cm long gray mark that contrasted sharply with the black body. The entire scratch feels like sandpaper with uneven edges. When wiped with a wet cloth, uneven dark spots appear in the middle of the scratch—that's a sign of metal starting to rust. Ordinary scratches don't behave this way. For example, if a small stone chips off the topcoat, the paint appears whitish but the primer remains intact, showing no color difference or rust spots. Now, every time I wash my car, I carefully inspect the scratched area. If exposed primer is found, it must be treated with rust inhibitor immediately. After all, with the metal layer directly exposed to rainwater, corrosion can eat through the sheet metal in as little as three months if it progresses rapidly.

[VanElisa]

From my experience, there are three typical characteristics of exposed primer: the color of the scratch contrasts with the original car paint, with the gray primer standing out noticeably on the colored surface; it feels rough to the touch, lacking the smoothness of the original paint; and if left untreated for a few days, it oxidizes and turns yellow. Last week, my neighbor's car got scratched by a tree branch, revealing silver-gray primer that looked like a patch against the red body. Unlike superficial scratches, areas with exposed primer cannot be polished back to normal—they require repainting to cover properly. Leaving it untreated for long can cause the edges of the steel panel to rust and bubble, and in severe cases, rust spots may spread beyond the exposed area. It's advisable to get it repaired as soon as you notice exposed primer.