Paint and coating applications have evolved by leaps and bounds over the years. Traditionally, paints were selected based solely on aesthetic appeal and durability. However, with the advent of new technologies there are several innovative and unique options to consider.
Ceramic coatings in particular have drastically changed the paint and coating landscape since their introduction in the 1970s. Several industries including oil and gas, construction, aviation, aerospace, automotive and electrical rely on ceramic coatings for a number of applications.
In this article, we will take a look at ceramic coatings and detail their most common uses across various industries.
What is a Ceramic Coating?
To understand the composition of ceramic coatings, we must first understand what is meant by a ceramic in this context. A ceramic is defined as an inorganic, nonmetallic solid material composed of metal or nonmetal atoms held in ionic and covalent bonds. A ceramic consists of metal or nonmetal compounds that have been shaped and hardened by exposure to high temperatures.
Ceramic coatings are paints infused with ceramic microspheres, which are microscopic round ceramic particles that are distributed throughout the coating solution. (Learn more about what goes into a paint in the article The Composition of a Paint Coating.)
As opposed to traditional coatings that contain up to 60% water, ceramic coatings contain a high percentage of solid microspheres. Therefore, most ceramic coatings are classified as high solids coatings since these microspheres occupy a significant portion of the solution by volume.
Due to their high percentage of solids, ceramic coatings are usually thicker and act as a more efficient barrier against extreme weather conditions when compared to oil and water-based solutions.
On the downside, ceramic coatings require more skill to apply. Methods such as detonation guns, oxygen acetylene powder deposition, chemical vapor deposition and plasma spraying are typical methods that are used to apply ceramic coatings to surfaces.
Common Applications for Ceramic Coatings
Ceramic coatings are quickly becoming a viable alternative to organic and polymer-based coatings for surface protection applications. Although organic coatings are generally less expensive than ceramic coatings and require less skill to apply, they possess limitations that make them unsuitable for use in specific environments.
Listed below are some of the most popular uses for ceramic coatings.
The tough outer shell of a dried ceramic coating chemically bonds to the metal substrate to form a passive and impervious top layer. This layer prevents air and moisture from coming into contact with the underlying metal. With oxygen (the cathode) and moisture (the electrolyte) out of the equation, the oxidation reaction cannot occur, and therefore corrosion cannot occur. This is a form of barrier protection.
In the oil and gas industry corrosion damage can cost millions of dollars every year. Pipelines and other offshore equipment are typically coated with ceramic coatings to prevent corrosion. This can help extend the equipment's lifespan, minimize repair costs and decrease maintenance downtime.
Ceramic coatings possess a high degree of hardness and a significantly low coefficient of friction. In other words, the coating allows components to “slide” over each other more easily, therefore reducing the amount of frictional force.
Some typical industrial applications for low friction ceramic coatings include pumps, chutes, conveyors, valves and ball bearings. (Related reading: Erosion Corrosion: Coatings and Other Preventive Measures.)
Ceramic coatings are classified as dielectric coatings, which mean that they are highly resistive to electric current, thus making them very suitable for electrical insulation applications.
Apart from the electronics and electrical industry, electrical insulation materials are also in high demand in the mechanical, industrial and automotive sectors.
Some components that are commonly insulated with ceramic coatings include:
- Handheld tools
- Electrical cable racks
- Contact bearings
- Engine components
Thermal Barrier Protection
Overheated metallic components are prone to failures such as thermal fatigue, warping and melting. Thermal barriers are materials that are applied to metallic surfaces operating at high temperatures. Ceramic coatings form an effective thermal barrier that limits the thermal exposure of structural components.
Ceramic coatings are known to withstand temperatures in excess of 1200°F (650°C) , with specially formulated composite ceramics withstanding up to 1600°F (870°C).
In the aviation industry, ceramic coatings are used to insulate turbine alloys from thermal cycling and melting. When used in conjunction with cool air, thermal barriers allow for higher internal combustion temperatures (higher than the melting point of the alloy in some cases) and greater turbine thrust efficiency.
In addition to its protective properties, ceramic coatings are also used for their naturally vitreous appearance. In the automotive industry, ceramic-based coatings are preferred over other types of vehicle coatings due to its ability to maintain a glossy finish over a greater length of time.
Moreover, vehicles coated with ceramic-based paints do not require frequent waxing and are easier to clean.
The glossy appearance and durability of ceramic coatings are also used in the dental industry for tooth repair to replicate a natural “pearly white” appearance.
The versatility of ceramic coatings makes them a viable alternative to traditional organic paints. In some cases, ceramic coatings offer several protective properties that overcome the limitations of organic-based paints. This allows ceramic coatings to be used in situations that are simply not suitable for conventional paints.
Although ceramics can be initially more expensive due to their higher material cost and the cost of equipment and skilled labor required to apply them, the reduction in the amount of maintenance and repair operations can result in significant cost savings over the long term.