No, spray paint is not waterproof in general.
Most types of spray paint will degrade if they are exposed to water, which is why graffiti can be cleaned off relatively easily.
Though with that said, there are various types of spray paint that are highly water-resistant, and some that are so waterproof that they can be used as waterproof sealants.
Generally, if you are buying spray paint that is supposed to be used outdoors, then it is probably highly water-resistant.
If you are buying specialist paint, such as that used to spray concrete ornaments and things like birdbaths, then it will say on the label if it is waterproof (and it probably is).
Wet Paint and Dry Paint
If you are spray painting a wooden cabinet, and you spray something you didn’t mean to, then you can probably get the paint off pretty easily by washing it if it is still wet.
This even includes paints that contain resins, sealants and varnishes, though you will probably need to use other chemicals like acetone to get it off.
Still, most varieties of paint are far easier to wash off (with water) if you do it when they are wet.
When spray paint is dry, it has bonded with the material it is used on and is more water-resistant than when it is wet.
This is not as true if you have sprayed something that the paint hasn’t bonded very well with.
For example, some paints bond very poorly with polished metal, and so even when dry, the paint may be pretty easy to wash off.
Otherwise, dry paint is more water-resistant, and when waterproof paint is dry, it is able to withstand an extended time tolerant to water and high humidity.
Different Types of Spray Paint
As you can imagine, the different types of spray paint have varying resistances to water.
Epoxy paint contains several adhesives and polymers, which makes them resistant to water, stains and chemicals.
Some epoxy paints can be fully waterproof but may still struggle to maintain integrity outdoors because they cannot handle abrasion, heat or frost very well.
Nevertheless, several types of epoxy paint are highly water-resistant, if not waterproof, which makes them useful for all sorts of applications.
High heat spray paints are used for things like ovens and/or outdoor items, and they are made of a variety of chemicals.
These include things like epoxy phenolic, silicone, epoxy novolac, a much more specialized multi-polymeric matrix.
Under all but the specialized circumstances (like where permeable paint is required), these are waterproof.
Chalkboard paint is commonly applied as a sprayed paint, and rather surprisingly, it is not very water-resistant at all.
In fact, they often absorb water, which is why when chalkboards are cleaned down, you can still see the wetness for some time after.
Chalkboard spray paints are made out of a variety of ingredients that include a mixture of talc, acrylic, glycol, titanium dioxide, water, carbon black, opacifiers, esters and silica.
If you need to then there are ways to waterproof chalk paint.
Frosted paint is very water-resistant, but it doesn’t take a whole lot to remove it if you expose it to hot water and scrub it a little.
Enamel paint on the other hand is very water-resistant because it is glossy fast-drying paint.
Not only is it waterproof (in most cases), but it will also withstand harsh weather pretty well too.
Acrylic paint is often used on cars and is usually finished by sealing it with a clear coat as a top surface/sealant because the acrylic paint underneath is not fully waterproof.
Once the sealant is removed, the paint will peel and bubble due to heat, cold, water and UV light.
Using a power washer on your car paint is a good idea if you are cleaning it, but you should wet the car first to lift off the sharper dirt and gritty granules.
If you spray the car without soaking it first, then the pressure of the washer can push the hard grit into the sealant.
This action can make scratches and dents in the sealant surface which enables water and the elements to reach the paint below, starting the corrosion process and causing damage in the long term.
Still, an oil-based paint on the right surface can make the surface fully waterproof for a fairly long time before repainting is needed. Rust preventative paints are almost always waterproof too.
Also Read: How Long Does Waterproof Spray Last?
The Application of the Paint is Key
Some paints only become waterproof if they are applied to the correct surface, and some need primer so that they bond correctly.
Even if you buy a waterproof paint, or use a highly water-resistant paint, it will not be effective (at least over the long term) if it is not applied correctly.
If water is allowed to get into whatever you have painted, perhaps through an area you didn’t cover correctly, then it will be affected.
It may swell, shrink, or degrade in a way that forces the bond between paint and surface to break.