Scratch Repair

Scratch repair (paint restoration) refers to an automotive detailing and body repair process designed to rectify surface paintwork damage caused by scrapes, branch scratches, stone chips, or vandalism through a series of machine compounding, chemical filling, or spot-respraying techniques. Original factory paint is typically a multi-layer system consisting of a cathodic electrodeposition layer (e-coat), primer surfacer, basecoat (colour coat), and clear coat. The core technical principle relies on accurately assessing the depth of the scratch—whether it is confined to the clear coat or has penetrated into the basecoat or primer—and adopting targeted methods to restore surface flatness and mirror-like gloss.

Core Process Classification and Technical Architecture

Depending on the depth and extent of the damage, the repair process is primarily categorised into the following technical approaches: 

Shallow Scratch Polishing and Compounding:

This applies to swirl marks, fine hairline scratches, or light branch scuffs confined strictly to the outermost clear coat (i.e. the fingernail test catches no distinct groove). Technicians utilise polishing compounds and finishing polishes of varying abrasive grades with a rotary or dual-action polisher and foam pads to micro-cut a minute layer of clear coat. This optically levels the scratch edges with the surrounding surface, effectively eliminating the defect and restoring the clear coat's mirror reflectivity. 

Medium-to-Deep Touch-Up and Body Filler/Primer Repair (Medium-Deep Touch-Up and Primer Repair): 

This applies to deeper scratches that have penetrated the basecoat or exposed the underlying primer and bare metal. For minor chipped areas, an OEM touch-up paint pen is typically used for precision filling and curing, followed by fine wet-sanding to level the surface. If the scratch is extensive or accompanied by a minor dent, the area must undergo spot sanding, body filler (putty) application for levelling, followed by primer, colour basecoat, and clear coat respraying, before being cured under infrared lamps and blended seamlessly via machine polishing. 

Safety Specifications and Physical Limitations

Strictly Prohibit Heavy Compounding Without Assessing Clear Coat Thickness (Prohibiting Excessive Polishing Without Measuring Clear Coat Thickness):

A vehicle's factory clear coat is remarkably thin—typically measuring just 30 to 50 microns (comparable to a single sheet of paper)—which means it can only endure a finite number of machine compounding sessions over its lifespan. Aggressive, unmeasured compounding must never be performed. Over-polishing in pursuit of instant perfection risks burning or striking through the clear coat entirely to expose the basecoat. Without the protective clear coat, the underlying colour coat will rapidly oxidise, fade, dull, and even delaminate or peel under prolonged exposure to UV radiation and rain.

Strictly Prohibit Inadequate Surface Preparation and Poor Colour Blending (Prohibiting Improper Paint Matching and Surface Prep Leading to Peel-Off):

Paint restoration is a high-precision craft demanding stringent dust control and exacting colour-matching accuracy. Substandard workmanship is unacceptable; failing to thoroughly clean residual grease, road grime, or surface rust from the groove prior to repair will cause the fresh paint film to bubble, crack, and delaminate under ambient temperature fluctuations. Furthermore, inaccurate colour mixing or neglecting proper edge blending (fade-out technique) will leave a noticeable "patchy" finish, severely compromising the vehicle's aesthetic appeal and used-car resale value.