Acid Washing

Acid washing is the process of washing a car in acid. This is done to remove metal fallout or contamination from cement, concrete or limescale. The car's paintwork is coated in acid, washed, and then the acid is neutralized using a mild caustic chemical. It is left on the car long enough to break down lime or eat away metal particles but not long enough to damage your paint, which is fairly resistant to acid.

There are now products on the market which are effective against metal fallout which are less harsh, however acid washing might still be used in cases of particularly heavy contamination and for the removal of limescale or concrete contamination.

What it means

Acid washing is the practice of cleaning parts of a car with acidic chemicals rather than neutral or alkaline shampoos. These products are formulated to dissolve mineral deposits, concrete dust, cement splatter, baked-on brake dust and other stubborn contamination that normal washing will not shift. They are usually sprayed or brushed on, allowed a short dwell time and then rinsed away thoroughly with water.

Why it matters

• Very effective on certain contamination: Acidic cleaners can remove limescale, water spots and some types of fallout that would otherwise need aggressive mechanical methods to shift.
• Speeds up heavy cleaning: On badly neglected wheels or vehicles exposed to building dust or concrete, a carefully controlled acid wash can save time compared with scrubbing alone.
• Higher risk if misused: Strong acids can etch glass, stain or dull paint, damage alloy wheel finishes and attack bare metals and trims if they are too strong, left too long or allowed to dry out.
• Not a routine shampoo: Acid washing is a special measure for specific contamination, not something that should be used at every wash.

Where you’ll see it

You may see the term “acid wash” or “acid wheel wash” on trade-only chemical labels and in some valeting or bodyshop procedures, especially for concrete removal, heavy water spotting or wheel refurbishment. Professional detailers are more likely to talk about using an acidic cleaner in a controlled way, often as part of decontamination on glass, wheels or heavily contaminated lower panels.

Context

Acid washing sits in the chemical decontamination category alongside alkaline traffic film removers, fallout removers and tar removers. Many modern detailing chemicals are formulated to be safer and pH balanced, but genuinely acid products are still used in niche situations. When they are used, they are normally followed by a thorough rinse, neutral wash and often some level of polishing or refinement to restore gloss and ensure any etching is removed or minimised.

Common mistakes

• Using strong acid washes as a regular car shampoo instead of a targeted decontamination step.
• Allowing acid products to dry on the surface or dwell for too long, leading to etched glass, dulled paint or damaged wheel finishes.
• Using brick acid or other construction acids on cars, which are far too harsh and can cause severe and sometimes permanent damage.
• Skipping proper rinsing and neutral washing afterwards, leaving residues that continue to react with metals, trims and coatings.
• Assuming “stronger is better” and over-concentrating the product instead of sticking to the recommended dilution and test areas.

Written by Danny Argent. Last updated 17/11/2025 17:26