METHOD OF PREPARING AND COATING ALUMINUM CYLINGER BORES

摘要

A method of treating a light metal cylinder bore wall to adherently receive a thermally sprayed metallic coating, that comprises (a) honing the wall to produce a net cylinder shape surface by use of spiral overlapping cross-abrasions having certain peaks and valleys of the abrasions folded over and molded to create tears, folds and undercuts rendering a hook and ladder effect, the honing being carried out with the use of a machining coolant to prevent burnishing of the walls; (b) either concurrently or shortly after step (a), washing the honed surface with a hot alkaline solution comprising (i) a non-soaping aluminate forming agent (sodium xanthate) that produces a residue on the walls, and (ii) surfactants that facilitate wetting of the walls even when some steam bubbles may be present; (c) rinsing the washed surfaces without disturbing the residue; and (d) thermally spraying a metallic bond coat and top coat on the honed and washed surface to render adhesion between the coating and prepared surface that is at least 5000 psi .