Bolts are usually very tiny and can be very difficult to paint. Some bolts are of a regular size but it is still not easy to paint them because they have grooves on the side. It requires a steady hand and a good kind of paint that does not chip off when the bolt is screwed on. The usual problem with painting bolts is that the paint comes off after the bolts are tightened. To prevent the paint from coming off, the paint must be meticulously applied to the bolt.
Sand the Bolt's Surface
It is important to prepare the surface of the bolt before painting. To do this you must sand the bolt in preparation for painting. The purpose of sanding is to make the surface smooth. Paint will adhere better when the surface you are painting is smooth. The bolt may not attach properly if there are lumps after it is painted. Sanding is important especially if the bolts are a little rusty. Sand the bolt with good-quality sandpaper until all the rust is removed and the bolt is again smooth and rust-free. To remove rust from hard-to-reach places, you may also use a steel brush.
Do not skip this part of the process of painting. The end result will greatly depend on how well you sanded your bolts before painting them. Once the bolts are all clean, it is best to wipe a little petrol on them to remove any remaining dirt or grease. Never wash or soak the bolts in water; this will only get them rusty all over again. Grease and oil will prevent the paint from adhering well to the bolts. It may peel or chip off when it dries.
After the bolts have been properly sanded, it is time to apply several coats of primer to them. Any ordinary paint will not do. It must be paint specifically for priming. Red lead is one of the best primers for painting on metals. Give the entire bolt a thorough coat of primer. You may even add another layer of primer once the first coat dries. This will give the bolt more protection against rust. It will also make the paint on your bolts last longer.
Finishing paint will not adhere well to the bolts if they are not primed first. Even if you decide to use a spray paint to apply the finishing paint to your bolts, you still need to apply a coat or several coats of primer to them.
Apply the Top Coat
Once the primer has dried, the top or finishing coat can be applied. You can use any kind of exterior paint that is of good quality so that it lasts longer. All your efforts to sand and prime the bolts will be wasted if you use low-quality finishing paint. There are also paints made specifically for metals. Acrylic latex paint is usually the best paint to use on metals.
Let the bolts dry for at least 24 hours before putting them back in. The common problem with bolts is that they usually lose paint after they are tightened. Some recommend putting masking tape over the bolt as it is tightened to protect the paint.