A scratch—should you polish it off or touch it up? The key is how deep the damage goes.
In a nutshell:If the primer is not damaged, polishing will suffice; if the primer is damaged, repainting is needed; a touch-up pen is only for emergency use and easily leaves marks.
I. Determining Depth (Light/Dark)
Clear coat only: No snag when scraped with a fingernail; can be removed by polishing.
Damaged to primer/base coat: Shows base color or white/metal exposed, requires repainting.
Exposed metal: Must be rust-proofed before repair, otherwise rust will reappear.
Figure: Determine repair method based on whether the primer is damaged.
II. Polishing Limit
Polishing only removes minor scratches on the clear coat layer. It is ineffective if the depth exceeds the clear coat thickness, and the clear coat gets thinner with polishing, so do not over-polish.
III. Touch-up Paint and Touch-up Pens
Damage reaching the primer should be properly repaired with paint (spot repair or local repair). Touch-up pen is only suitable for emergency use on very tiny spots; hand application easily causes runs/sagging, color mismatch, and lacks clear coat protection, and long-term outdoor exposure will cause faster deterioration.
Figure: Clear coat scratch polishing, deep scratch standard touch-up paint.
Path suggestion: Shallow scratches → polishing; deep scratches → spot repair / local repaint and clear coat; exposed metal → apply epoxy rust prevention first then repair. Paint pen is for emergency only, not a permanent solution.
Summary
Scratch repair depends on depth: if only the clear coat is affected, polishing is possible; if the base coat is damaged, standardized spot painting followed by a clear coat is required; if metal is exposed, apply rust prevention first. Touch-up pens are for emergency use only, prone to color mismatch and runs, and are not suitable as a permanent solution.
Frequently Asked Questions (FAQ)
How to determine the depth of a scratch?
Lightly scrape with a fingernail; if there is no snagging and it is only in the clear coat, it can be polished. If the base color, white, or bare metal is exposed, it means the damage has reached the primer or even the steel plate, requiring paint touch-up or rust prevention first.
How deep a scratch can polishing remove?
Polishing only removes fine scratches in the clear coat; it is ineffective if the depth exceeds the clear coat thickness. Also, the clear coat gets thinner with each polish, so repeated excessive polishing should be avoided.
Can a touch-up pen be used?
Only suitable for tiny spots as an emergency. Hand application tends to drip, shows obvious color mismatch, and lacks clear coat protection, so it deteriorates faster outdoors over time and should not be considered a permanent solution.
How to handle scratches that expose metal?
First sand to remove rust, apply epoxy primer for rust prevention, then add primer/base coat/clear coat; otherwise moisture intrusion will cause rust bleed and bubbling.
What is the safest way to deal with deep scratches?
Use standard spot touch-up or local repainting, and reapply clear coat for protection; for large areas or difficult blending, refer to local repair process to treat the entire panel.
Kexin New Materials · Automotive Coating Technology Library | This article is technical Q&A content, for reference in selection and application
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