摘要 |
A cast iron exhaust manifold having an inside surface covered with a ceramic coating comprising, by weight, about 30% to about 70% unfused silica, about 5% to about 30% magnesia, about 5% to about 20% alumina and about 3% to about 10% sodium oxide. The coating will preferably be built up in multiple layers at least one of which is relatively porous and another is relatively dense resulting from vacuum degassing of the slurry used to deposit the coating.
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