| After-treatment control technique, especially catalytic convert is an effective method to solve the increasing serious atmospheric pollution from the automotive exhaust particularly. The poor coating binding strength between the metallic substrate and the washcoat has attracted more attention by the most researchers.The coating technique of theγ-Al2O3 based ceramic washcoat on surface of FeCrAl metallic substrate was investigated in this paper, partly including the pretreatment condition of the metallic substrate and preparation of slurry. The washcoat quality was measured by SEM, XRD, EDX, BET, ultrasonic vibration and thermal shock test.The results of the pretreatment of the metallic substrate show that the optimal pretreatment condition is oxidized at 950℃for 10h and the metallic substrate surface performance is obviously improved after pretreatment. The transition layer grown on the surface of FeCrAl metallic substrate during such pretreatment increases the specific surface areas and coarseness of the surface of FeCrAl metallic substrate, which improves the combination ability between each other. Moreover, the metallic surface element distribution is improved and Al diffuses towards the interface and forms oxidation transition layer preferentially with oxygen while Fe and Cr in the opposite direction.Adhesion and loading percentages of washcoat primarily depend on the variables of slurries employed in the coating process. The results show that the achievement of satisfactory adhesion and loading percentage can be obtained by the adequate slurries: pH about 4.0, particle sizes of d90 below 10.00μm, CZ/Al2O3 ratio about 30% and solid content below 35 wt.%. The formulation ensures satisfied loading percentages and good adhesion of the washcoats, meanwhile enhances the washcoat uniformity and thermal stability of the coating.The washcoat prepared with above method has excellent properties of ultrasonic vibration, thermal shock test and high surface area.
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