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Black Annealed irin coils
Tutu yiyi dudu annealed coils (CRBA), tun mo bi "Blue Irin".CRBA jẹ atutu ti yiyi irin coilsti o ti jẹ oxidized nipasẹ annealing ni fifi sori ẹrọ pataki kan lati le ṣe agbejade Layer magnetite tinrin pupọ (Fe304) lori dada (kere ju 1 μm nipọn) fun aabo diẹ sii.