Thermal Coatings by Don Redmon

Thermal Coatings
-Don Redmon
The following is a brief and general customer’s guide to Thermal Coatings. Thermal and friction reducing applications are applied after the part is etched. The part is cleaned, the coating is applied and then oven cured. This insures that the application, unlike paint, is tougher and more than skin deep.
The semi-gloss black external coating is a Thermal Dispersant, it gets rid of heat faster and more efficiently than bare metal, it also sheds mud and rubber. Typical applications are cylinders, cylinder heads, intake manifolds, brake calipers, radiators and oil coolers. Always properly warm up your engine before operational loading. It will now take longer for your engine to come to operating temperature. Clean with soap, water and/or light solvents, do not leave it to soak in a solvent tank.
The silvery looking Thermal Barrier coating keeps heat from passing through it. It is applied to piston crowns, combustion chambers, valve faces and exhaust pipes, to name just a few uses. This coating will raise the working temperature inside of the combustion chamber. We suggest that you start with a colder range spark plug and watch your readings, this is especially important the smaller the bore size. Clean carefully, do not scrape the surface, polish with extra fine steel wool using light pressure.
The dark gray application is a Dry Film Lubricant. It is used on piston skirts, bearings and valve springs. This is the softest of the coatings and depending on the clearances, it will visually wear. Use light compatible oil when installing a piston in a cylinder. Remember though that the applications are more than skin deep.
Depending on engine modifications, your location, air pressure and quality, etc., you may need to re-adjust or re-jet your engines fuel and ignition systems. Do this carefully, i.e. richer and retarded is better to start with. Always err on the side of caution, it is much less costly. Please do not hesitate to call with any questions you may have.

Hello, my name is Don Redmon and I am the owner of Replika Maschinen, Inc. We are an airflow, porting, engine and thermal coating facility located in the Santa Cruz, California area. I have been professionally involved in the racing, high performance and technical automotive and motorcycle markets for over a quarter of a century.

I was recently honored when asked to write a column for "Speedoptions.com". This column will cover a wide variety of technical subjects and I welcome your comments and suggestions for possible future columns. If there is something of a technical nature you would like to know more about, let us know. In the meantime you can expect to see future articles on:Engine blueprinting, what it is and why I should care.Cylinder heads, competition valve jobs, various stages of porting, and types of porting.Thermal coatings, cryogenics, various types of dynamometers and what the differences are.Turbochargers, superchargers, nitrous oxide, where these devices come from and what we should be doing with them.We will also talk about camshafts and the largely ignored valve spring. I will get into basic subjects such as gasolines, octane's and both pump and racing fuels and why you should care. What the differences are between gasoline, methanol and nitro methane. Multi valved and multi camed cylinder heads, fuel injection, how new is this technology really, and where it comes from.

But most of all, this column will be about information. There are many products and services out their vying for your hard earned dollars. Some products and services are good choices while others are less than good or less than optimum for what you are trying to accomplish. Only when primed with some basic knowledge and hopefully the spark to seek out additional information, can you then venture forth, as a better-informed and more questioning consumer. Therefore, our first topic will be about selecting symbiotic and workable combinations, a continually overlooked but very important aspect of engine building. As we are an air flow/ porting facility, we deal with many different types of internal combustion engines and racing disciplines. Two strokes for motocross and road racing, four strokes, high output and high revving automotive and motorcycles, Imports to big cubic inch Domestic V-8's. We even work with low revving, very high torque, large capacity diesel engines improving power and fuel efficiency. However, no matter what we are doing or whom we are working with we hear the same story again and again, a story every shop in existence has heard and experienced frequently. It goes like this: The consumer calls or comes in with a box of different parts all by different manufactures. The customer then proceeds to ask to have this menagerie assembled into an engine that will propel his vehicle into the 6-second zone.

Marketing in this country is an art form. If you doubt this, consider the pet rock, or grass growing plaster gargoyles and professional wrestling. We are the world leaders in marketing and packaging of products. My point here is that just because something looks good, comes in a great package and promises you straight teeth and a better sex life, it does not mean that it is what you need in your particular car or that it will work with your particular engine combination. Engines, like people, are made up of various component parts. These parts must work in harmony in order to receive the greatest return from the effort put into them. The better the parts work together, the greater the harmony, the greater the output of power. Trying the throwing mud at the wall and then seeing what sticks approach to component selection is not a wise path to follow. So before you buy, formulate a plan of action as to what you want to sensibly achieve and what you can afford to achieve. Then, contact the companies and shops you would like to be working with on your project and ask their advice. Contact others and get their advice, read about your engine, go to the races and ask questions. Then, with your engine builder's help, make sensible realistic decisions and purchases. Always purchase quality components. Remember you get what you pay for.

At Replika Maschinen, inc. our primary business is improving airflow and volumetric efficiency primarily via porting of the engines air passageways. However, we also seek to improve volumetric efficacy by improving the quality of the air or fluid charge by lowering the temperature of that charge to gain more oxygen per volume. Air is the working fluid of internal combustion engines, so air is the fluid I am referring to here. When we lower the temperature of our working fluid/air, it becomes more dense. One of the ways in which we lower the temperature of the inlet charge and engine and achieve this volumetric advantage is through the world of THERMAL COATINGS. Around the end of the Second World War the need to go higher, further, faster enveloped the defense and aeronautical industries. These desires spawned a metallurgical revolution in exotic materials. But along with these exotic materials for air frames and more powerful engines came new problems of protection. Corrosion resistance, noise suppression, friction reducers, thermal barriers and thermal dispersants were invented or modified to address these new concerns. The automotive racing industry discovered these substances sometime in the 1970's. However, as they soon learned, racecars and their engines are not jet-propelled aircraft and vice-versa. Coatings that worked just perfectly in the sustained and controlled environment of aerospace often meet its match in an automobile engine. Zirconia based ceramics for example, have very different expansion rates, 4.16x10-6, when compared to aluminum alloy at 13.7x10-6 over temperature ranges of 80 to 800 deg. F. Fortunately there were individuals who saw the benefits and worked hard to develop coatings specifically for the automotive industry. These are what we here at Replika Maschinen, inc. and other facilities around the world use and are what we will concern ourselves with as the topic of conversation to follow.
Turbo Compressor Housing

But first, what are thermal coatings and what do they do? Thermal coatings come in two basic categories; thermal dispersants to help get rid of heat and thermal barriers to block heat. Thermal dispersants help the coated part shed heat faster than that part normally would dispense with were it bare or un-coated. Thermal dispersants are generally exterior coatings and therefore primarily work via convection, but conduction is also involved. Convection is the transfer of heat by the laminar or turbulent motion of a liquid or a gas from one region of space to another. The convection style transference of heat as it relates to the automotive type world would include radiators, oil-coolers, brake calipers, rotor carriers and hubs, exhaust systems, turbocharger/supercharger housings and air and liquid cooled engines. Conduction is the transfer of thermal energy through a material or between two bodies in contact. This would apply to heat transfer between cylinder and cylinder head or any two or more parts in contact with one another. So for our pop quiz, which theory of thermal heat transference covers lap dancing.
Miata 1.6 Cylinder Head

THERMAL DISPERSANTS as the name implies, reduce or remove excessive heat. As mentioned earlier, a large majority of an engines potential heat energy ends up as waste. An engine must dispense with this excessive heat or else burn up. Coated cylinder heads dispose of excessive heat at a far greater rate then un-coated heads. Reducing the onset of engine killing detonation, lower intake charge temperatures and less chance of blowing head gaskets due to cylinder head warpage and walk are just a few more advantages. Engines work on heat but this heat must be properly dealt with. Too little and the engine will not operate in an efficient manner, too much and it will melt down. In early 1998, the INDY LITES organization decided to conduct a test of their then current oil cooler and thermal dispersants. They had the oil cooler thermal dispersant coated, it was then tested on and off the track. They experienced a 15% reduction in oil temperatures; the smaller older coated oil cooler out performed its newer and larger replacement. All INDY LITES teams now run coated oil coolers. In NASCAR, Bill Elliot and many others, run coated radiators to help reduce internal engine and engine bay temperatures and improve aerodynamics via smaller radiator openings. Brake parts and systems can also be coated. Obviously the faster heat is dissipated the less likely the chance of fade or out rite failure. As a side benefit, coated parts shed dirt and rubber and are far less likely to plug up, as readily as un-coated parts will. In our next article, we will discuss Thermal Dispersants and Dry Film Lubricants. Thanks, until next time, Don Redmon, Replika Maschinen, inc.
Stop Making Sense Thermal Coatings Part II Article by: Don Redmon (Friday, May 18, 2001) (522 reads)


Extra High Temperature Thermal Barrier Coated Expansion Chamber In part 2 of our article on thermal coatings, we will discuss Thermal Barriers and Dry Film Lubricants. Thermal barriers as the name implies are barriers or shields to thermal events or heat. An internal combustion engine is basically a thermally controlled air pump. So various engine events will depend on heat to function properly while others depend on the elimination of heat to live. Remember, an engine's working fluid is air, introduce an air charge into the combustion chamber, provide an ignition source with a combustible compound to heat it at the correct time, and you produce work. Sounds easy, however heat is the key to making a little power, a lot of power, or seizing the engine. Heat as it relates to a high performance racing engine is different conceptually from what is wanted by a smog controlled street engine. While the conceptual differences are there, as are the reasons for each argument, the results are similar. Combustion efficiency produces more work with less fuel and less residual emissions. Areas to hold heat into include, the combustion chamber and exhaust systems and areas to shed heat include most everything else. On the intake side, the cooler the intake air the more dense the air charge. However, there are instances, EPA, CARB environmental controls, evaporation levels of certain fuels, that demand higher but moderated temperatures. Controlling the heat of the combustion process and the exhaust elimination system can assist in maintaining control over both engine interior and exterior temperatures. An engine certainly does get hot under the hood. Studies have documented temperature drops of 100 to 300 degrees of under hood heat. What do you think dropping under hood temperature 100 degrees does to your inlet charge temperatures? Barrier coatings on exhaust system components contain the heat into the system and preclude the heat from just migrating around the semi-closed container called your engine bay. By controlling this engine heat, we put it to work for us in the area of power increases instead of simply an ambulatory road kill grill. I am sure you have all heard the term ceramics applied to automotive-coated parts. While ceramics are used in automotive applications, their use is still relatively new and cutting edge. In the "1980's" I remember magazine articles and talk about an "Oval Track" style "Midget" engine, designed, built and run using ceramics and plastics in place of steel and aluminum for internal engine parts. Ferrari and other Formula One teams are currently using ceramics in both engine and suspension applications. But for the average guy or gal on the street, their use is minimal outside of thermal barriers. Barrier coatings do contain amounts of ceramic but they are not pure ceramic for one very important reason, coefficient of expansion. Aluminum alloy for example, will expand at 13.7x 10(-6th) while zirconia based ceramics expand at 4.16x 10(-6th) in the temperature realms of 80 to 800 degrees Fahrenheit. Aluminum obviously expands at a far greater rate than does the ceramic, which makes it hard to keep them in contact with each other for very long. While steel headers for example, will expand less than aluminum, steel is still affected by heat more than and therefore its expansion rate is greater than the ceramic too. Coating pistons, valves, combustion chambers, turbocharger exhaust manifolds and turbine housings, exhaust ports, and exhaust headers and pipes is where thermal barrier coatings most useful work is done. Keeping the combustion heat into the combustion chamber where it belongs and not allowing it to migrate throughout the engine is important. As exhaust gas speed and wave intensity is directly related to temperature elevation and the consistency of the temperature throughout the length of the pipe. Maintaining elevated and constant temperature throughout the length of the system is paramount to effective scavenging and evacuation. Thermal barriers hold that heat into the system helping it to perform better and also protecting the coated parts from rust corrosion and premature damage. So where does all of that internally combusted heat go to? It goes to the same places it normally does but now we are trying to control and positively use the normally wasted heat energy. Normally, part will go into the cooling system to be eliminated via the radiator or in the case of air-cooled engines, cooling fins. Part will go out the exhaust system as additional waste. The remaining thirty percent or less is actually used to produce work and turn the crankshaft. It should not take a rocket scientist to realize that increasing the latter's percentage even in small amounts will garner additional returns in work and power. Here at Replika Maschinen, inc., we have found that coated pistons will stave off the damaging effects of uncontrolled excessive combustion chamber heat, detonation and/or pre-ignition. This could ordinarily lead to a hole in the piston in two strokes and/or ring land damage in a four-stroke engine. Thermal barrier coated pistons transfer less heat to wrist pins, cage bearings and the general crankcase area. Thermal barrier coated intake and exhaust valves will not transfer their normal amount of heat directly to the valve springs, hence the springs last far longer than normal. As the valves themselves do not get as hot, they do not wear the respective valve seat contact areas as quickly, parts last longer with less heat. Thermal barriers will not totally prevent engine damage caused by tuning errors that lead to severe detonation and or pre-ignition. They will not improve your sex life, eliminate problems caused by general ignorance and/or help from your friends who know everything or create world peace. However, they will protect vital internal engine components far longer and provide an extended range of extra protection when things do go wrong. By coating these parts, we hold the heat in to where it belongs, the combustion chamber. We gain usage of more of the potential and available BTU's (British Thermal Units a system of measuring heat potential) to use in order to convert our inlet charge to work. Heating the air to turn the crankshaft translates into the potential for more work and power. Dry Film Lubricants and friction reducers are lubricants that maintain themselves in a dry state. Friction is a force that resists motion between two bodies or parts in contact with one another. Lubrication is necessary to reduce friction and prevent metal to metal contact within your engine's various moving parts. A thin film of oil, sometimes only ". 000025 of an inch" thick is all that holds your engine parts apart and moving. Dry films work and provide protection at all times, however, they provide special lubricity and extra protection when combined with liquid lubricants. You might think of dry film lubricants, as you would think of freeze dried foods, you add liquid to make them work even better. Dry films are a mix of various very slick materials, in a resin-bonded matrix. The application process is similar to thermal coatings and the lubricants are imbedded into the metal. Dry film lubricants are designed to reduce friction, which produces heat. They also reduce metal to metal interaction and wear. Reducing friction in piston skirts, valve springs and bearings extends their life and lowers the engines overall friction coefficient. This again translates into more power at the crankshaft instead of negative parasitic power losses. Dry films also assist during break-in periods, less wear means less metal residue in the oil pan, etc., etc., etc. As dry film and friction reducing lubricants are bonded into the metal, under extreme conditions and duress, they remain in and on the parts long after grease or oils have burned away.