Ceramic additives to paint for insulation

Discussion in 'Metal Boat Building' started by mikeny, Aug 14, 2015.

  1. mikeny
    Joined: May 2013
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    mikeny Junior Member

    Anybody out there actually use these new ceramic products to for condensation I see now Michael Kasten recommends for his steel boat constructions I put some in the bow chain locker then put a five pound block of ice on deck and I did not get any condensation but I'm still very skeptical has anybody else out there actually use this stuff and had a good result
     
  2. MikeJohns
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    MikeJohns Senior Member

    It's a common query. The concise answer is that it depends :)

    Whether you get surface condensation inside depends on the inside air temp and humidity, and the outside temp. The dew point is the temperature the air needs to be cooled to at which the water will start to condense.

    For insulation to prevent condensation when the outside temp is at or below the dew-point there must be a temperature gradient across whatever material is acting as insulation. It has to be sufficient to keep the interior surface at a higher temperature. If the paint is only a few microns thick and there is a large difference in temperatures it can't achieve this unless the surface is rough enough to trap a layer of air (that's a minimum of coarse sandpaper roughness).

    Dew points can range around 10 to 25 C ( 50 to 75 F ). If you had a very small range of temps, say the interior at 20 degrees C and the exterior at 19 C and the dew point between, then the paint has a fighting chance of doing something.
    The heat conductivity of the paint is the critical figure. Just how well it works depends entirely on this figure and it's not really what would be classed as insulation even at an inch thick (and you are putting it on at a few hundred microns).

    Water can condense in very small beads (dew) You don't actually see this dew very well by eye except on polished surfaces. Whether larger beads of condensation form depends on the ongoing humidity and how far below the dew-point the surface is and how the air circulates close to the surface.

    An objective test would have a block of ice on the test paint and a block on the normal paint. Or you could just measure the interior surface temperature with a simple handheld IR thermometer, there really are only two factors; insulation properties ( thermal conductivity) and surface roughness, there's nothing else.
     
  3. Angélique
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    Angélique aka Angel (only by name)

  4. philSweet
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    philSweet Senior Member

    Actually, these paints are designed to have high reflectivity and low emissivity, particularly in the thermal infra-red region. That is how they reduce the total heat transfer. They add nothing to the R-factor.

    It is a complicated issue, especially if you are talking about corrosion. In a locker, you want to keep the peak temperature as low as possible so that the peak dewpoint is as low as possible. You want to have as small a total heat transfer over the course of the day, and you want the rate of temp change to be small. And even then, none of this much matters unless you have some amount of ventilation going on.

    The usual application is as a white, thickish roof coating that reflects solar radiation. True insulating paints are very good at reflecting thermal wavelengths, so they can be used in the middle or on the inside surfaces as well, however, it makes more sense to use them on the outside of the thermal mass if the structure has a lot of mass compared to the contents.


    The biggest problem is advertising claims. There are standards and RIMA has done testing on many commonly advertised coatings. NASA can certainly produce a paint that performs well, but the commercial market seems to be counting on the fact that most people have no way of gauging the effectiveness of the stuff. Beware that many of them use aluminium powder as well.

    EDIT I did find one product that is trying to differentiate itself from the class of reflective coatings described above. It specifically stated it was not a reflective paint, but rather was intended for insulating things. It was applied very thick - 5mm and up.
     
  5. mikeny
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    mikeny Junior Member

    Thanks guys for the input I'm still not sure why they seem to still be pushing this as a insulation I guess I'm back to spray foam with fire retardant foam I don't know what else to do I just hate to cover up all the steel
     
  6. Poida
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    Poida Senior Member

    I was engaged in the coatings industry at one stage of my varied life.

    We had some insulating paint (ceramic powder stuff) and got it tested.

    The coatings specialist at the testing lab said he had never seen any difference between ceramic paint and ordinary white paint. All of the manufacturers of that reflective paint use white paint. Theoretically the thickness of the paint can't contain enough ceramic to make a difference.

    After I left the coating industry I saw at a home show someone demonstrating an insulating paint. There was a heat source above two sheets of roofing steel. One was a white insulating paint, the other was grey. Not an accurate demonstration of its effectiveness.

    Poida
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Mica was used in paint, presumably for its reflective ability. I can even remember old toasters with mica sheet to reflect back the heat from the wire filament.
     

  8. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    The stuff in the op seems like all the other stuff, just a paint additive. The op concoction is a water based mix, how long can that last?
    I'm kind of wondering about the claim that slight-moderate heating can accelerate corrosion, especially if something is coated to block out air.
    Scientist and researchers can shuck and jive with the best.
     
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