What is a paintable ceramic or high-temperature coating?
Our coatings consist of binders or suspension agents, vehicles, and fillers like any commercial house paint. The binders are added to “glue” the main ingredient material to the substrate. The binders are typically organic, inorganic, or a mixture of these. A suspension agent is used to hold the main ingredient in a suspension to keep it from settling out. The vehicle is the liquid that is used for the paint, generally water or a solvent. The filler is the main component of the paint that will be left after the paint is dried.
After painting a surface or substrate with our coatings, they are heated up to high-temperatures where the resulting adherent coating protects the substrate or imparts some desired surface property.
How do paintable ceramic coatings compare to chemical vapor deposition (CVD) or plasma sprayed coatings?
Paintable ceramic coatings are typically around 50 to 60% dense (or have 40 to 50% porosity) and are applied like house paint. Plasma-sprayed coatings are applied with a VERY high-temperature plasma (over 20000 degrees) and are generally around 85 to 90% density. CVD coatings are 100% dense. CVD coatings are generally very thin – less than 0.001 inch; plasma-sprayed coatings are typically 0.005 inch to 0.050 inch; ceramic paints are often applied 0.002 to 0.010 inch.
Are paintable ceramic coatings temporary or permanent?
Paintable ceramic coatings are often used in areas where they last for a given time and then require re-coating. The lifetime of a coating quite dependent on the many variables; use temperature, atmosphere, coating thickness, shop practice, and many other factors. The lifetime is different for every area of use and place of use.
How much material will evolve from the coating and will it affect my process? Is there a “cure” required?
Our paintable ceramic coatings are designed with minimal outgassing in mind. Thus, there is always very little material that will evolve from the coatings when they are heated up. No special cure is needed: the coatings are merely dried and placed into their high-temperature use. The slow evolution of the small amount of volatiles generally does not cause any problems.
How do I apply these ceramic coatings?
Our paintable ceramic coatings are quite easy to apply. Just think of them like house paint – applied by brushing, dipping, or air-spraying to metals, ceramics, or graphite substrates.
How do I dilute these coatings?
Test coatings at full strength initially and then dilute up to 15% if required. This works for most coatings, although BN Hardcoat, Coverguard, and some others should not be diluted at all for best results.
Some of the coatings can be diluted much more: see the individual datasheets for directions on dilution. Water-based coatings can be diluted with water. Solvent-based coatings can generally be diluted with ethanol or acetone.
What thickness do I need to apply?
The general “rule-of-thumb” is to apply the thinnest coating that you can use. Or, a little is good; a lot is not. The reason for this rule is that thicker coatings have a greater tendency to “mud crack” on drying as well as to spall on thermal cycling. We recommend thicknesses from 0.002 to 0.008 inch for most of our coatings.
Can I apply these coatings by dipping?
Dipping can be done but is not recommended since it leads to a rather thick coating that must dry from the outside first. This can lead to residual/underlying moisture that can lead to spalling (coming off) of the coating.
What temperature and atmosphere can I use these coatings?
Our coatings vary in their specifications for use-temperature and atmosphere (see the individual datasheets). However, we have coatings that can be used
to over 2000 C in most any atmosphere.
If I use an aerosol coating and want to scale up its usage, what can I do?
We offer “aerosol brushables” of each of the refractory materials that have been used in our 13-oz. aerosol cans:
- boron nitride
- titanium nitride
These “aerosol brushables” are a bulk paint form which allowa the aerosol coatings to be economically scaled up.
How do I order these coatings?
The coatings can be ordered online or by telephone (865-482-5717), FAX (865-482-1281) or by email () using a company purchase order or using American Express, VISA, MasterCard or Discover.
Is the coefficient of thermal expansion (CTE) important in matching with the substrate that I am using?
Generally, with paintable ceramic coatings, this is not a very important consideration. The paintable coatings are very “forgiving” for different substrates, because of the way the main ingredient is bonded to the substrate and because of the porosity of the coatings. The thinner the paintable coating is applied, the more “forgiving” the coating is towards CTE mismatches. The use-temperature is also a consideration: IF the use-temperature is below 600 C, the thermal expansion problems are generally not an issue at all.
What is the range of thermal and electrical conductivity of these coatings?
The highest thermal conductivity coatings are those of Boron Nitride (which has the same thermal conductivity as steel and is considered VERY high thermal conduction for a ceramic. The lowest thermal conductivity coatings are Zirconia based.
Coatings with the lowest electrical conductivity are those of Boron Nitride or Alumina. The highest electrical conductivity coating are Titanium Nitride based,but the “effective” electrical conductivity is still limited due to the binder material. Therefore, paintable coatings (even of TiN) should only be considered as being modestly electrically.
Are these coatings suitable for wear applications?
Paintable coatings are not good for wear applications requiring high toughness and abrasion-resistance: CVD or plasma-spray coatings are the ones for those areas. Paintable coatings are great for stopping corrosion (not erosion) that is often confused with “wear” areas.
How can porous coatings such as these protect against high-temperature corrosive attack by gases?
By having closed porosity and very fine porosity which has a “tortuous path” for the gases to penetrate in order to attack the substrate, our selected paintable coatings can stop gaseous or vapor attack for metals or graphite. They DO NOT stop attack and penetration from liquids.
Do you provide samples of the products?
In general, we do not provide samples since the coatings essentially look and act like housepaints, so there is little to gain from use of just a small sample. Often, we recommend that customers purchase an aerosol-can first to see if these coatings are right for their use.
How do the Brookfield viscosity numbers compare to commonly used items – as a way to get a feel for the thickness of the liquid paints?
Viscosities of these common materials should give a comparison with our Brookfield numbers/ranges given on the technical datasheets for our coatings:
- Water = 1 centipoise (cps)
- Thin-Medium Milkshake = To 600 cps
- Thick Milkshake = To 1300 cps
- Very-thick Milkshake = To 3900 cps
- Honey/Karo-Corn-Syrup = 2000 – 3000 cps
- Blackstrap Molasses = 5000 – 10,000 cps
- Ketchup = 50,000 – 70,000 cps
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