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TYPE SC and Type SC-1400
These water-based
coatings result in hard, abrasion-resistant coatings that have
high-emissivity and are usable on all graphites/carbons like
ordinary housepaint. The TYPE SC coating inhibits graphite oxidation
to its maximum recommended use-temperature of 1000 C, whereas TYPE
SC 1400 provides protection extended to 1400 C and even to 1600 C
for short-time use. Fired compositions of the coatings [TYPE SC
listed first/ SC-1400, second]: 75%/72% silicon carbide; 8%/8%
phosphorus oxide; 6%/6% alumina; 6%/6% silica; 5%/4% boron oxide;
0%/4% mullite. These compositions result on heating to above 600 C,
at which point the coating is fully outgassed, whereas curing occurs
by 350 C [i.e., a full-high hardness, water-resistant coating occurs
at the cure temperature after approximately a 5-minute hold], and
whereas some glazing occurs at 1100 C/1400 C for SC/SC-1400
coatings.
Both of these greenish-gray-colored coatings have a
specific gravity of 1.85 and a pH of 2-3 in their liquid form ?
utilizing a sol gel suspension agent/binder. TYPE SC and TYPE
SC-1400 have medium viscosity and can have a 300-400 sq.ft. per
gallon coverage ?generally painted onto a lightly-roughened,
cleaned graphite surface as 2 to 3 brush-applied layers. It should
be noted that, after the first coating, fast-brushing is needed to
avoid rewetting/washing-off the first coating when applying
additional coatings; or, the coating can be cured before applying
additional coatings to avoid the rewetting/washing-off effects.
While these coatings are designed for air usage, they are usable in
all environments and are excellent in cyclic use. |
