A crack in plastic may be properly repaired by welding and repainting. However, this type of repair is expensive and requires a professional. If the crack in your plastic does not require extensive repair, you can easily conceal a crack in plastic using simple household and store-bought items.
Step 1: Put on Protective Gear
Put on safety goggles, gloves and a mask. Cover the work area with old newspapers or a disposable plastic tablecloth. Work in a well-ventilated area, as some plastic fillers and epoxies may emit noxious vapors.
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Step 2: Clear the Damaged Area
Clear the damaged surface of the plastic, removing decorative or protective pieces that may prevent access to the crack. Trim any pieces of plastic protruding from the crack. To stop the crack from spreading, drill a small hole at the end(s) of the crack. Sand the damaged area with medium-grit sandpaper.
Step 3: Brace the Back Side
Apply bracing, such as tape, on the underside of the damaged area, if accessible, if the crack is severe or wide. This gives the patching materials a surface to adhere to as you fill and repair the damaged plastic.
Step 4: Clean the Surface
Clean the surface of the plastic with a degreaser to remove oil residue, plastic fragments and dust. This will provide a clean surface to which the plastic filler or putty can properly adhere. Allow to dry completely.
Step 5: Prepare Plastic Epoxy
Prepare the plastic epoxy putty, carefully following the manufacturer's directions. Be mindful of the curing time for the epoxy putty — some epoxy putties have short curing times, so try to complete your work within that timeframe, working quickly but methodically. You may also use a plastic filler in place of the epoxy putty.
Step 6: Apply the Epoxy Putty
Push the putty into the crack and spread the putty over the damaged area using a flat mixing paddle or any sort of implement that can be used as a trowel. Smooth out the putty using the paddle.
Step 7: Remove Excess Putty
Trim or remove the excess putty. Allow the putty to cure and harden.
Step 8: Sand With Fine-Grit Sandpaper
Lightly sand the patched surface using fine-grit sandpaper. Remove all traces of dust. If necessary, apply a second coat of putty in the same manner as in the previous steps.
Step 9: Paint With Primer
Apply one coat of all-purpose alkyd primer using a paintbrush. Allow the primer to dry. Alternately, use a plastic primer spray.
Step 10: Prepare a Paint Color
Choose a paint color that matches the color of the plastic. If no paint color matches the color of the plastic, mix two or more acrylic paint colors to get a color that matches the color of the plastic.
Step 11: Apply Acrylic Paint
Apply acrylic paint with a brush or use a spray paint formulated for use on plastic, adding extra coats of paint if necessary. Allow each coat to dry before applying the next coat.
Step 12: Sand and Polish
Gently sand the painted surface with fine-grit sandpaper. Remove all traces of dust. Apply a light coat of auto wax or furniture polish to the patched area using a clean cloth.
Things You'll Need
Safety goggles, gloves, dust mask
Old newspapers or plastic tablecloth
Electric drill and drill bits
Sandpaper, medium- and fine-grit
Plastic epoxy putty or plastic filler
Alkyd primer or plastic primer spray
Auto wax or furniture polish