Stahl Explains: What is a coating or paint? Are they the same?
What do you know about chemicals? Are they essential in our everyday life? Is there something like ‘good’ or ‘bad’ chemicals? In our series ‘Stahl Explains’, our chemists and researchers will give clear answers to most frequently asked questions. This week, André Derksen answers the question if paint and a coating are the same:
Everybody knows what paint is, because of the use at home, but not everybody knows what a coating is. Actually, paint and coating often mean the same, but coating has a more industrial ring to it. A paint functions to both protect the article and it also functions to decorate it, by a certain color or texture. In the arts, a paint has only decorative effect when a painter paints a painting. The primary use of a coating is to protect the article on which it has been applied, but of course, this coating can be colored and can be dried with a certain texture, which results in a decorative effects as well.
For paints, it is often understood that these are liquids, whereas a coating can also be in the form of a gas or solid, although most coatings are liquids as well. Paints are sometimes sold in spray cans, so they may appear as gaseous, but these are in fact liquid paints that have been pressurized using a gas.
A paint or coating is a mixture of components:
- a carrier (water or solvent or both) that will evaporate during the drying of the coating, although there are also some coating that are ‘100%’
- a binder (a polymer, examples are alkyds, polyurethanes, oils, natural or synthetic) that is the film forming component in the coating,
- other components that are often but not always present:
- pigments or dyes that add color
- hiding pigments to make the coating non-transparent (so that the surface or color underneath is not visible anymore)
- fillers, which are added to give extra volume or extra solids to the coating
- flow agents, anti-foam agents, anti-settling agents, UV-stabilizers, biocides, which are added in small amounts to improve certain properties
A coating is applied in a thin layer on a substrate and the coating is then dried or cured at either ambient conditions, or with exposure to heat or light. The dried coating layer has smaller thickness than the applied ‘wet’ coating layer. The thickness is usually between a few micrometers to several hundred micrometers. A coating layer often consists or several thinner layers, which can be layers of the same coating mixture, but can also be consist of different types, for example: primer layer, base coat, top coat, protective coat.
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