Article Updated: May 2022

This exhaustive article focusing on protective coatings and sealants will address the various functionalities, materials, application processes as well as some properties. The protective coatings and sealants market continues to grow worldwide and we will see why this trend is not expected to subside anytime soon.


In the early days of manufacturing and the dawn of the industrial age, components were made to last a long time. Steel was in scarce supply and so were other metals such as aluminum, and so planned obsolescence was a term unheard of and neither was the popularity of the term protective coatings and sealants. There was a huge demand for almost anything manufactured, such as appliances, vehicles, toys, kitchenware, plumbing and electrical items, etc.

Because of the insistence of the market to produce only long lasting goods, engineers and designers generally designed with higher margins of safety. Gage thickness of metals used even in machine covers, appliance guards was high; oversize fasteners were used almost everywhere, I-beams and construction elements were designed with significant margins of safety. Even to this day, you can hear the term “they don’t make it like in the olden days” almost everywhere.

However, as manufacturing roared, more raw material industries cropped up and metals such as steel and aluminum were available in plenty and manufacturing machinery came online at full speed.

This led to excess capacity and planned obsolescence concepts were introduced. Thus it was deemed easier to get rid of an item rather than repair and reuse. Goods were manufactured only to last for a limited time and if they had be replaced quite often, then the cost had to be brought down.

This pricing pressure led engineers and designers to reduce gage thicknesses and compensate the design discrepancy by putting on protective coatings to enhance life. Hence a component which was originally built with a .100” thick piece of metal that constantly faced sliding wear, was replaced by a .025” thick piece of metal with a thin plasma sprayed tungsten carbide coating that lasted about the same time.

The need for protective coatings and sealants did not end there. What we have described thus far is only one facet. What was even more of a challenge in manufacturing was that components were designed to work under more severe conditions than ever before. This led to severe demands on design engineers that could not be met with old technologies.

For example, aircrafts had to fly faster, carrying higher payloads and travel longer, with inter-continental flights being the order of the day. Hence aerospace components could not simply be used in the bare machined or formed state. They demanded sophisticated coatings such as thermal barrier coatings and other protective treatments to enable such long periods of exposure to severe conditions.

Homes and factories were getting built in areas of inclement weather to house the world’s rising population and growing number of factories. This meant roof coatings to enhance roof life. Factories needed non-skid floor surfaces leading to floor coatings and sealants.

Advances in technology, including the advent of computers and computing devices demanded conformal polymeric protective coatings and sealants as well as glass coatings for screen surfaces and protective coatings for solar panels.

And as technology and industry advances are made, the demand for these high tech protective coatings is bound to increase for many more decades. Hence this is a high growth industry by any measure of business.

The Breakdown:

Protective coatings and sealants can be broken down into two major categories: Functional Ones and Decorative Ones. Functional coatings are used to enhance the surface properties of components sometimes and at other times they are required to enable the surface of a component to have significantly different properties than the bulk material. We will deal with these in detail further below.

Decorative coatings on the other hand are used simply to make the part look beautiful from an aesthetic stand point as the primary objective and some protective features as a secondary objective. Your bathroom faucets, metallic cell phone covers, automotive exterior colors, etc fall under this category. We will address these also.

Thermal Spray Coatings:

Thermal spray coatings form a family of coatings that meet the definition of functional protective coatings and sealants to a T. They enable the deposition of highly sophisticated materials into a variety of substrate materials.

The substrate materials can be steel, titanium, Inconel, aluminum, plastics, etc. The materials coated can be metallic, ceramics and cermets. Commonly applied thermal spray coatings include nickel-aluminum, cobalt-nickel-chromium-aluminum, yttrium, tungsten carbide-cobalt, chromium carbide-nickel-chromium blend, nickel-graphite, aluminum, aluminum-silicon, copper-nickel-indium, yttria-stabilized-zirconia, aluminum oxide, chromium oxide, etc.

Methods of application include air plasma spray, twin wire arc spray, single wire combustion spray, high velocity oxy-fuel spray, low pressure plasma spray and detonation gun process.

Briefly stated, the process comprises of cleaning the part surface, masking to cover up areas where the coating is not to be applied, abrasive grit blasting to roughen the surface, application of the coating by one of the methods outlined above, de-masking to remove the masking materials, deburring to remove the sharp edges making the part ready to ship after inspection.

This family of coatings is used to provide thermal protection to components that operate under high temperature conditions such as aircraft combustion chamber liners, wear protection such as aircraft blades, vanes and shafts, high temperature sealing surfaces such as aircraft knife edge seals and their mating parts, insulative surfaces such as in automotive oxygen sensors, pump and valve components, printing rolls, etc.

Correlating coating materials and applications, yttria-stabilized zirconia is used for thermal barrier applications, copper-nickel-indium for fretting wear, aluminum oxide for knife-edge seals, nickel-graphite for knife-edge-seal mating surfaces, cobalt-nickel-chrome-aluminum-yttrium for aero engine stators, tungsten carbide-cobalt for sliding wear resistance, aluminum for bridge structural elements, etc.

Thin Film Vapor Deposited Coatings:

In the world of protective coatings and sealants, thermal spray coatings are considered to be “thick” coatings: thicknesses being of the order of .008” to .012” generally and upwards of .050” for nickel-graphite and stator segment CoNiCrAlY coatings.

On the other hand thin film vapor deposited coatings are less than .002” generally speaking. There are two general methods of thin film deposition: chemical vapor deposition and physical vapor deposition. Both these techniques are newer technologies in the time scale, from a production stand point.

In chemical vapor deposition, various pre-cursors enter a chamber that is heated to a relatively high temperature ( in the case of aluminum oxide coatings, chamber temperature is of the order of 1,000 C or 1832 F ), where chemical reaction takes place to form a solid thin film. The parameters of gas flow rates, chamber pressures, etc need to be closely monitored to form the perfect thin film.

In physical vapor deposition, the coating material is physically vaporized and deposits onto the substrate to be coated. Chamber pressures are usually very very low.

Coatings of Titanium Nitride, Titanium Carbonitride, Titanium-Aluminum-Nitride, Aluminum Oxide and Nickel Aluminide are very popular; the first four being heavily used in the metal cutting inserts, drills and end mills industry and the last one being heavily used in the aero engines industry for oxidation resistance.

Zirconium Nitride, Aluminum, Aluminum-Titanium-Nitride and Chrome Nitride are popular decorative finishes produced by physical vapor deposition that are heavily used in faucets, expensive watches, aircraft interiors, etc.

Paint, Plastisol and Powder Coatings:

These coatings are dualistic in nature; they are used both as functional coatings in some applications and decorative protective coatings in other applications.

For example, paints protect interior and exterior surfaces of homes, exterior panels of machinery, etc. Powder coatings are used heavily in automotive exterior finishes, machine tool covers, doors, etc. In this instance, one could see them as decorative finishes.

But there is an entire world of paint and powder coatings that are used for functional effects. For example, certain colloidal paints are used for their very low frictional characteristics. Paints of molybdenum sulfide fall into this category. Teflon powder coatings are used for their electrical insulation and low friction properties.

Stricter environmental laws have boosted the powder coating industry quite a bit, because in this process electrostatic methods are used rather than volatile organic compounds for the propulsion of the pigment. Of course, one cannot powder coat a kitchen or bathroom wall and paints still rule that kingdom!

Plastisols, especially PVC plastisols form conformal coverage for tools, handles, etc. But they also find tremendous use as abrasive grit blasting boots, covers and the like.


The world of sealants is huge. They find tremendous applications in various situations. For example, sealants are used for sealing off moisture in basement walls, so mold is kept away. Adhesive sealants find application in bathrooms to seal off water from seeping through cracks and crevices. Polymer based concrete sealants are used in cracks to prevent moisture and water seepage especially if there is significant concrete movement. There are cases where sealants are used to keep off dust and sound.

Then there are the exotic ones. Some silicone formulations are used in anti-graffiti applications. I know of a paper converting and printing machine manufacturer that gets his aluminum rolls plasma sprayed with nickel-chrome-aluminum-yttrium and seals the coating with a silicone release agent. This allows the rolls to have anti-stick properties.

Most sealants will have a thixotropic material that allows for control over the viscosity of the sealant. Fumed silica is one such material. Sealants are also used in some hazardous applications, such as thread sealants for fasteners used exposed to chlorine gas, which is highly dangerous.

Platings and Conversions:

There are two basic kinds of plating: electroplating and electroless plating. In the former electricity is required and in the latter, no electricity is required. Gold, silver, nickel, copper, etc can be plated onto substrates.

Nickel plating is quite common. Nowadays, HVOF chrome carbide competes well as a hard chrome replacement coating for functional applications, because it does not deal with carcinogenic hexavalent chrome that is prevalent in chrome electroplating. Most of the chrome plating used in the aerospace industry is being replaced with electroless nickel plating.

While zinc plating is possible and is used in some cases, for many applications, galvanizing by the hot dip process is quite economical and functions well. Because of its sacrificial nature, galvanizing provides extended life for components.

Conversion coatings are the case where the surface of a component gets converted to a different compound. The classic is the anodizing of aluminum, whereby the surface gets converted to aluminum oxide. Anodizing can come in various colors. Sometimes, Teflon impregnated hard coat anodizing is used to offer additional lubrication properties to the component processed.

Buy or Sell Protective Coatings and Sealants:

If you are an engineer, purchasing agent or designer looking to purchase coating services or if you are a salesman, distributor or supplier of coating services trying to expand your customer base, you can benefit by signing up with for free!

Here is the brief step by step instructions.

Step 1: Click Sign-In, Create a New Account, Enter Your Details, Email, etc.

Step 2: If you SELL coating services, enter the Company Product and Services Screen, Choose Industrial Products and Materials, Coatings and Surface Treatments, Thermal Spray or appropriate services you offer, choose a geographical radius in which you want to sell and choose a secondary email address. That’s it. You’re done !

Step 3: If you SELL something else, enter the Company Product and Services Screen, Choose the appropriate category for the products your firm sells and choose a geographical radius in which you want to sell those and choose a secondary email address. That’s it. You’re done !

FP in Action: Anytime anyone searches for whatever you sell in the main search box and enters the details of the search, YOU – the supplier will get an email instantly. So if you sell Thermal Spray services and someone searches for it, you will get notified. Similarly, if you are a valve distributor, when someone searches for that, you will get notified.

So you can search for the appropriate coating service you need by searching in the search box AFTER registering.

Thus you can offer your services as well as buy products and services without spending money on ads, helping your sales team AND your purchasing team at once with one registration.

Your competitors may already be on garnering business quietly under the radar !

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