Restore and paint a classic car underside and hidden metal

Classic underside restoration

Guide to restoring and painting a classic car underside and hidden metal

A classic car underside often combines old coating, surface rust, bare metal, boxed sections and hidden cavities. The job needs stripping where needed, rust sealing, epoxy primer, tough protective coating and cavity sealant for areas that cannot be reached after assembly.

What do you need to restore and paint a classic car underside and hidden metal?

Stripping and cleaning

Mipa Quick paint stripper, Mipa Paint Stripper Spray and Mipa silicone remover help remove old coatings and contamination before the underside is rebuilt.

Rust preparation and sealing

MP Fine sanding pad removes loose corrosion, Miparox anti-rust spray treats firmly adhering rust, and Mipa Rust Sealant penetrates and seals rusted metal before further coating.

Epoxy primer base

Mipa EP primer filler with EP Hardener E 25 normal and Mipa EP Thinner creates a corrosion resistant primer base on prepared metal.

Tough black protective coating

Mipa Protector black and Mipa Protector 2K Spray create a robust textured black coating for high wear underside and chassis areas.

Hidden cavity protection

Mipa HV cavity sealant in aerosol probe format or sprayable 1l format protects enclosed sections with a wax based film.

How to restore and paint a classic car underside and hidden metal

  1. 1
    Strip weak old layers

    Remove failing paint, underseal and old coatings where adhesion is poor, then clean the surface thoroughly.

  2. 2
    Prepare the metal

    Sand loose corrosion away and clean the exposed metal before rust treatment or primer.

  3. 3
    Seal rusted areas

    Treat firmly adhering rust with the rust spray or rust sealant, then let the surface dry as directed before coating.

  4. 4
    Prime and protect

    Apply epoxy primer where a primer base is needed, then protect exposed underside areas with the black protective coating.

  5. 5
    Seal hidden cavities

    Use cavity sealant with the probe or sprayable format inside boxed sections, seams and hidden metal after the main structure is prepared.

Which classic underside method should you choose?

Visible underside coating

Use the epoxy primer and Mipa Protector method for exposed underside sections that need a tough painted protective finish.

Hidden metal protection

Use the HV cavity sealant method for enclosed sills, boxed sections and seams that need wax protection inside the structure.

Aerosol detail repairs

Spray formats are useful for local underside repairs, small access areas and classic cars where gun access is limited.

Technical details

  • Mipa EP primer filler is the epoxy primer stage and uses EP Hardener E 25 normal with EP thinner for the system method.
  • Mipa Protector 2K Spray is a robust 2K polyurethane acrylic protective coating for underbodies, chassis and heavy duty surfaces.
  • Mipa HV cavity sealant uses a wax based protective film and the aerosol version includes a probe for enclosed sections.
  • Mipa Rust Sealant and Miparox anti-rust spray are used before final coating when rust remains after mechanical preparation.
  • Paint stripper should be kept away from sound coatings that do not need removal and must be cleaned off before refinishing.
Practical suggestion

Plan the underside in zones before opening the first can: stripped metal, rust sealed areas, epoxy primed areas, protective coating areas and hidden cavities each need their own timing.

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