When most people think of coatings they think of the paint on their car or the walls of their house, when in fact many everyday things you see have a coating.  Some coatings are for protection while others have a decorative purpose.  Some coatings, like the ones on your car, have a two fold purpose:  1)to protect the surface of the car from rusting and 2)to make the car look shiny and cool!

So what is the definition of a coating?  Well a coating is defined as a composition, which when applied in thin layers, forms a non-tacky, adherent film that hides, protects, and/or decorates the substrate.  Was does that mean?  Basically when the paint is applied, it sticks to the surface, it doesn't stick to anything else, and it protects, hides and decorates what you painted.  There are many different types of coatings, but they can be broken down into 2 broad categories:

        1:  Architectural or trade sales or Do-It-Yourself (DIY) -  These are the paints for
           the weekend warriors, like you and I, that can be purchased at our local hardware
           stores.  Where we can actually apply the coatings to our house or lawn furniture
           and they dry in the air.

   2:  Industrial or Original Equipment Manufacturers (OEM) -  Coatings in this
   category usually require machines or baths to apply the coatings and ovens or UV
   light for them to "cure" or dry.  These coatings are applied buy the producer of a
   particular product.  The coating on the vehicle below is an example of an OEM coating.
 
 

DIY	OEM

• polymers (sometimes referred to as the binder or resin)
• pigments
• additives
• solvents (on some occasions)

The pigments are used to hide and give color to the substrate.  Pigments are either organic or inorganic fillers that are added to the polymer and solvents after the polymer has been synthesized.  Some of the pigments used in coatings are:  titanium dioxide, zinc oxide, iron oxide, carbon black,  phthalocyanine blue, and toluidine red.

Additives are the smallest portion of the overall coating, but can have the largest impact.  One usually thinks of a coating formulation in terms of its major components such as pigment, resin, and solvent.  However, a coating simply will not work without a number of key coating additives that must be used.  Additives are used in smaller amounts of <0.1-1 lb/ gal of coating.  Some additives are:  thickeners and rheology modifiers, defoamers, dispersants (dispersing aids), surfactants (surface active agents), mildewcides and bactericides, coalescing aids, driers, and anti-skinning agents.

A component that is used in some occasions is a solvent.  Solvents were originally used in all coatings, but with emergence of environmental legislation solvents have been reduced and in some cases eliminated.  Solvents are used to reduce the viscosity of the coating enabling the coating to flow like a liquid and they can be applied by brush, roller, spray gun, etc. Current regulations limit the amount of solvents used in coatings today and there is a stronger push for environmentally friendly coatings.  Some of the solvents that have been used in the past are: xylene, butanol, propanol, methyl ethyl ketone (MEK), butyl acetate, hexanes, and methylene chloride.

Now just adding these above components together may give what you think is a coating, but you have to test it to see if it is good enough to qualify as a coating.  Everybody have there own opinion about what makes a good coating, but the final test are the test themselves. Click here to see the types of tests that are done on coatings to determine their performance.
 

Now you know a little about the coatings used for just about everything.  As you walk through your life and look at everything, think about what is  coated:  clothes, paper, aluminum cans, roads, signs, walls, cars;  coatings are all around you.

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