Testing spray paint products on lantern hoods

Discussion in 'Fettling Forum' started by ColinG, Jun 27, 2020.

  1. MYN

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    I find it noteworthy to know and understand a little further, the compositions of heat resistant paints/coatings. Basically, they'd contain the primary functional materials as any paints, namely, pigments, binders, extenders/fillers, solvents and propellants in aerosolized products.
    As to how heat resistant are the paints, it'll depend on the properties of all the components that would remain in the coating after the solvents have dried off or evaporated.
    For instance, we have the VHT matt black stove, engine and exhaust manifold paints. Typically, the basic ingrdients would be as follows:-
    1. Carbon black and copper-chromite black spinels as the pigments. Both of them are highly resistant.
    2. Silicone resins as the heat-resistant binder.
    3. Talc, perhaps as the paint extender to smoothen, acts as some form of filler and barrier against moisture penetration into the substrate. It is mainly a magnesium silicate mineral and also quite heat resistant once dried/dehyrated after curing.
    4. A variety of organic solvents such as toluene, xylenes, methyl and ethylbezenes, acetone, etc.
    5. Carbon dioxide or butane, propane, etc gases under compression as the propellants.
    Items 1, 2 and 3 would still remain in the coating after drying and curing.
    The weakest point here would be the binder: silicone resin. Although it has a higher heat resistance compared to most other not-so-heat-tolerant organic binders, such as alkyds, epoxies, acrylics, polyurethanes, vinyls, etc., its primary functional component is a silane, comprising of silicon and hydrogen. Its the hydrogen that makes it less refractory, just like the way it behaves when in combination with carbon for organics.
    Therefore, no matter what is being stated on the label of many such products (vht, resistant up to 600/800deg C, 2000deg F, etc), the figures are at best, intermittent because silicones and the best epoxy resins would only withstand continuous temperatures in the range of 180 to 250 deg C. Only the pigments, fillers and extenders would bear the continuous heat on a typical lantern hood.
    I'll say in my current opinion(could be proven otherwise, anyway), the only paints that'll make it would need to have purely inorganic materials without the hydrogen being bonded within the binders.
     
  2. george

    george United States Subscriber

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    I personally don't think any of these paints will hold up to the high temps of the lantern tops. Only time will tell but all of the ones I've tried just didn't make the cut! Some of these paints are touted as being able to hold up to 1000 deg F and they may last for several light ups but eventually they start to show the affects of the intense heat. Hopefully a company out there will find an answer. Meantime, baked on enamel appears to be the best bet.
     
  3. MYN

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    I've had similar experiences, George. My current thoughts about these are pretty much the same as yours.
    But even 'enamels' could have a wide variety of meanings and might just refer to normal paint instead of the vitreous enamel. Some of the paint-enamels require a bake-cure to make them harder and more heat resistant. Still, I've not found any of them being able to withstand continuous(not just intermittent) temperatures in excess of 600deg C, which I'd say, a prerequisite for these to enter the qualifying rounds.
     

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