How does concrete and cement damage cars?
Concrete contamination can significantly damage vehicles in three main ways.
1. Surface Etching: When cement is setting, there is a chemical reaction which is caustic and corrosive to your car's paintwork. This will likely etch the paintwork, leading to damage to the uppermost surface, so even when the cement is removed, there will be a dull mark or staining. This is most obvious when cement powder contaminates a car and then becomes wet. The resulting effect is the same as hard water spots, only usually far worse.
etching at x50 magnification. [source: Acid Etch Resistance of Automotive Clearcoats. I: Laboratory Test Method Development]
2. Scratches and Scuffs: The abrasive nature of concrete mix can scratch paint and glass, either during contamination or while trying to remove it.
3. Undercarriage Damage & Corrosion: Vehicles driving through freshly poured concrete experience undercarriage contamination. This can cause additional wear on moving parts due to mechanical abrasion, and contribute to accelerated corrosion.
The Corrosive Nature of Cement
Many of the ingredients of cement, such as lime, calcium sulphate, and fly ash, can damage car paintwork primarily due to its caustic and corrosive nature. Lime, often present in the form of calcium oxide (CaO) or calcium hydroxide (Ca(OH)2), can have detrimental effects on the vehicle's paint when it comes into contact with it. Here's how lime can damage car paintwork:
1. Chemical Reaction: Lime is highly alkaline, and when it contacts the car's paint, it can react with the paint's clear coat, breaking down the binders that hold it together.
2. Concrete Etching: The alkaline nature of lime can cause surface etching on the car's paint or clear-coat. This results in the formation of small, shallow pits or dull spots on the paint surface, giving it a rough, dull and matt finish.
3. Discolouration: On older cars with solid colour conventional paint, lime can cause paint discolouration, leading to faded or altered paint colours. This is particularly problematic when lime-containing water or materials are allowed to dry on the car's surface under sunlight.
4. Staining: Lime may leave behind stubborn white stains or deposits on the car's paint. These stains can be challenging to remove and usually require wet-sanding and polishing to remove them.
5. Prolonged Exposure: Prolonged exposure to lime or lime-containing substances can worsen the damage over time. Rainwater or moisture can exacerbate the corrosive effects of lime on the car's paint, as caustic compounds are re-wetted and become corrosive again.
Written by Danny Argent. Last updated 25/01/2024 12:15