Are ground and plasterers, operating high-quality plaster before painting. The primer can deduce the wall surface plasterers 'to zero' and at the same time to prepare it for painting. For mineral substrates are mainly used acrylic paints. Diluent is water for them, so the acrylic paint 'breathe' – leak air and water vapor. Application of primer paint work required technology, on almost every pack paints can be found manufacturer's recommendations in this regard.
Often the manufacturers recommend for their use of paint primer of the same production. This ensures compatibility of the soil and basic colors. There are also colors, not requiring prior use of the soil, but they are few. On metal surfaces the situation is different. Primer needed on metal for better paint adhesion, but many kinds of paints on metal do not require prior priming. Moreover, there are paints that can be painted on the rust.
This is not about what you can paint directly on chipping rust layers. Layers need to clean off, but the small red rust for this type of paint is not hindrance. There are a primer for rust. In the case where no surface appearance is important, but you need to protect it from corrosion, rust on the bottom two layers will be the perfect way out. And finally, consider some general principles of painting, both known and not. The surface should be clean and dry. If it is re-painting, the loose pieces of old paint, cleaned with a wire brush. If the old paint does not peel off, it can leave, but if it is glossy or varnished, it is necessary for a better sanding link the new layer. The best results are achieved by applying at least two coats of paint (in addition to soil). In that case, when produced without the use of paint primer, paint the first coat should be thinned a bit. More liquid paint the first layer is well absorbed into the surface, which will help to better consolidate topcoat. Than diluted, depending on the type of paint and is always written on the packaging. The second and subsequent layers are applied only after the complete drying of the previous one. When painting wood by brush or roller to be led along wood fibers and prevent sagging. With skillful use of good results can be achieved with the use of the gun.