If the paint isn't sticking to the plastic, the problem is usually that the surface is too glossy. Thoroughly sand the plastic to a matte finish for best results. Keep the spray light to avoid drips. An initial tack coat of about one-third to one-half coverage will help later coats stick better.
Wipe off any dust with a clean cloth. Use a Primer: Apply a plastic primer if your paint requires it. This helps the paint stick better to the plastic surface. Allow the primer to dry completely before painting. Apply Paint: Use thin, even coats of paint, allowing each coat to dry before applying the next.
Plastic is one of the more difficult surfaces to paint because of its smooth surface, and plastic responds to temperature more easily by expanding and contracting, so it's more prone to cracking or flaking over time.
Sand the Surface to Create a Rough Texture for the Paint to Adhere To. Sanding is an essential step for ensuring good paint adhesion. It creates a slightly rough texture on the plaster wall or door, providing the paint with a better surface to grip.
To paint plastic effectively, you must have a good-quality paint and primer that will both ensure you get long-lasting, beautiful results. When it comes to paint for plastic, our experts always recommend Zinsser Allcoat Exterior as the best, especially for the average DIY'er.
“The best way to apply spray paint to a plastic surface is to always clean first and then lightly sand the piece if there are loose debris. Then, use Krylon Fusion All-In-One spray paint for the best adhesion!”
When spray painting plastic that is soft, like vinyl, a flexible paint is required, and acrylic-based paints and urethane modified acrylic paints adhere better without cracking, flaking, or peeling. Overall, oil-based paint isn't a good spray paint for plastic as it doesn't bond well.
Improper preparation such as not cleaning the walls or using the wrong type of tape can lead to problems with adhesion. Additionally, some surfaces may require a coat of primer before painting, while old paints or primers can also lead to trouble getting your paint to adhere correctly.
Painting and Staining
The acidic qualities of the vinegar will clean and degrease the surface and help the paint adhere. Odors: When applying paint of any kind, keep small dishes of vinegar around the room to absorb paint odors. Keep the dishes out for a few days, adding new vinegar each day.
Because, most likely, the surface you are spraying is high gloss plastic. Like any other high-gloss surface, paint does not bond well with it. You need to sand the surface, likely to about 300–400 grit so that the paint has a nice surface to hold on to. You can further protect it by clear coating.
PEELING PAINT AND POOR PAINT ADHESION
To fix it, start by using a paint scraper to remove any flakes, peels, or old, loose paint from the surface. Then with a putty knife, cover the area with spackle and allow it to dry.
Standard exterior gloss paint is a suitable finish for plastic when used in conjunction with an appropriate primer and undercoat. Either acrylic or oil-based gloss can be used, and both are available in a wide range of colours. Typical application methods include brush, roller and spray.
If the paint isn't sticking to the plastic, the problem is usually that the surface is too glossy. Thoroughly sand the plastic to a matte finish for best results. Keep the spray light to avoid drips. An initial tack coat of about one-third to one-half coverage will help later coats stick better.
Acrylic paint is a water-based paint that is popular for use on plastic surfaces. It is easy to clean up, dries quickly, and is available in a wide range of colors. Acrylic paint is also resistant to fading and chalking, making it a great choice for outdoor projects.
With our Matt Varnish acrylic lacquer, you also have the option of painting your plastic without a primer. Especially on surfaces that are hardly exposed to stress, such as doors or window frames, you can usually do without a sealant.
The application of Vaseline, a brand of petroleum jelly, creates a protective barrier which prevents the paint from adhering to unwanted areas and reduces the risk of peeling or chipping along the door's edges.
White vinegar contains acetic acid, which can soften the bond between paint and wood. Now, this isn't some miracle agent that will melt the paint off in seconds—vinegar doesn't work like a chemical stripper. But with a little patience and the right approach, it can certainly help.
Mixing vinegar and baking soda causes an immediate chemical reaction. This reaction forms water, sodium acetate (a salt) and carbon dioxide – the fizzy part. The amount of carbon dioxide gas that is produced from baking soda is remarkable – one tablespoon (around 18 grams) can release over five litres of gas!
After a part is thoroughly cleaned and conditioned, an important next step is the application of a primer coat. The primer serves a dual purpose in paint adhesion—protecting a metal substrate from corrosion and bonding the topcoat of paint to the substrate.
Lightly sanding the surface helps to remove any existing gloss, roughen the surface slightly, and create a better bond for the adhesion spray paint. Additionally, applying a primer or sealer to the surface further enhances adhesion by providing a suitable base for the adhesive paint.
Over time, as the painted surface ages, it will become less flexible and less capable of withstanding the stress and constant movement (expansion and contraction) in the substrate. The destructive result is loss of adhesion through crazing, cracking, flaking, peeling or blistering of the paint system.
Prime the Surface
If painting interior plastics, apply a high-adhesion latex stain-blocking primer. For outdoor plastics, spray-prime with specialized primers formulated specifically for adhesion to plastics.
From my interpretation of your question, you are looking for a clear primer or adhesion promoter. PlastiCote makes a product they call clear primer and adhesion promoter. Rustoleum makes a clear primer spray as well. Both products are intended for automotive use, but are claimed to work well on most plastics.
Surface contamination such as dirt, oil, and grease. Polish residues on the surface, which impair the adhesion of the paint. Excessive movement of the substrate, such as joints, imposing stress on the paint film which can result in cracking which in turn lets in moisture, ultimately resulting in a flaking paint film.