What Causes Bubbling in Original Car Paint?
4 Answers
Bubbling in car paint may be caused by internal rusting, but the primary reason is due to moisture remaining on the surface before painting. The topcoat layer of car paint has relatively strong sealing properties, especially with two-component paints after complete curing. If moisture is trapped within the paint film, it becomes difficult to evaporate. Subsequently, under high temperatures, the underlying moisture expands, causing localized stress on the topcoat film and resulting in bubbling. Here are additional details: 1. Bubbling after touch-up painting: Poor quality paint is often used in low-cost paint jobs; Additionally, if the paint application is too thin, exposure to weather conditions can lead to bubbling or cracking. 2. Important notes: Bubbling should not be ignored as it affects appearance. If left untreated, the topcoat may eventually crack, allowing rainwater to penetrate and cause metal rusting, which can expand the damaged area and harm the car body. Therefore, upon discovering paint bubbles, it's essential to visit a professional repair shop or 4S store for expert repair. For larger bubbling areas, complete repainting may be necessary.
Last time I washed the car, I noticed a few small bubbles on the hood. I talked to the experienced mechanic at the auto repair shop about it. He said that if paint bubbles appear on a new car, it's most likely due to improper primer treatment during production—rust spots or grease on the metal surface weren’t properly cleaned before painting. Another possibility is that the sealant at the sheet metal joints wasn’t applied well, allowing rainwater to seep in and lift the paint. This is especially common in coastal cities like ours, where the salt in the sea breeze acts like tiny knives, targeting weak spots in the paint. If you encounter this issue, never pop the bubbles yourself. You need professional equipment to sand down the bubbled area and reapply three layers of paint. Otherwise, within six months, it’s guaranteed to spread into large patches of peeling paint.
My garage queen just underwent bubble repair for its paint job. When the mechanic peeled it open, the metal substrate was covered in speckled rust spots—he called it electrochemical corrosion. A micro-battery forms between the metal and paint, with rainwater acting as the electrolyte, oxidizing iron particles over time until they swell and lift the paint. Special warning for street-parked cars under trees: tree sap mixed with bird droppings eats through clear coats. Last year, my neighbor’s roof got a back full of acne-like bumps from acidic oak tree sap. Treatment requires grinding corrosion layers completely, ideally with epoxy primer as an oxygen barrier.
As mentioned in a car magazine feature, paint blistering occurs when ionic activity between the body panel and contaminants (rust or pollutants) generates expanding gases upon moisture penetration. It commonly appears near high-temperature zones like hoods or door drainage holes, where significant day-night temperature differences cause repeated moisture condensation. Used car dealers dread this issue the most – repairs require infrared lamps for precise temperature control during baking, as a 20°C+ difference between new and old paint layers will cause cracking. A certain German brand even faced scandals when excessive humidity in their painting workshop led to batch blistering on vehicles after three years.
