Why are there so many types of coatings?
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 explains the why there are so many different coatings:
A coating functions as decoration, as protection or both. However, the same coating cannot be used for all types of surfaces or articles. There are surfaces that are very hard, like metal or stone, or very soft, like rubber or leather. On a metal surface it is often best to use a coating that is also very hard, because impact resistance and abrasion resistance is then very much desired. However, when that same hard coating would be used on a flexible surface like rubber or leather, it would not be suitable anymore. That is to say, if the substrate can be bent or squeezed, the coating should be of similar flexibility. If a hard coating is used on such a flexible substrate, the coating will crack upon bending or flexing. So, for a flexible substrate it is desired to have a coating that is also flexible after drying. Using this flexible coating on a hard surface does not pose a problem concerning flexibility, but unfortunately such flexible coatings usually cannot provide the desired protection to such hard surfaces, such as impact resistance, abrasion resistance, chemical resistance or corrosion resistance.
The type of binder in a coating is also an important choice. Some coatings are used outdoors and other coatings are used indoors. Some coatings will be exposed to lots of sunlight or very high or very low temperatures. The coating must be able to withstand these conditions for a certain amount of time/years. Some binders are very resistant to such extreme conditions, but coating manufacturers do not always choose these very resistant binders for a number of reasons: often these very resistant binders are more expensive, or they need a certain amount of solvent, which is undesired when used indoors.
A coating can be delivered in various forms. It can be a solution in a solvent, like the paints for exterior wood. It can be a dispersion in water, such as paints for interior stonewalls or interior wood. A coating can also be in powder form, which is used in industrial applications such as metal coatings for bed frames or automobile metal parts.
In the end, the type of coating is mainly defined by the different requirements of many specific substrates and specific uses.
Want to know more about coatings? Read our Stahl Explains:
'Is there such thing as natural coating?'
'What would happen if there were no coatings?'
'What is a coating or paints? Are they the same?'
'How do we design our coatings?'
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