Method of treating light metal cylinder bore walls to receive thermal sprayed metal coatings

A method of treating light metal cylinder bore walls to adherently receive a thermally sprayed metallic coating thereon, said treatable walls carrying a film of grease or oil resulting from machining operations, comprising;

• (a) honing said walls to produce a near net shape cylinder surface having spiral overlapping cross-abrasions with some peaks and valleys folded over and molded to create surface tears, folds or undercuts rendering a hook and ladder effect, said honing being carried out with the use of a machining coolant to prevent burnishing of said walls;
• (b) either concurrent therewith or following step (a), washing said honed surface with a mildly alkaline solution comprising (i) an aluminate forming agent that produces an aluminate residue oh the walls and (ii) surfactants that provide for wetting of the walls even when steam is present in the solution;
• (c) rinsing the washed surface to remove the solution except for said residue;
• and (d) thermally spraying onto said washed and rinsed surface a metalized bond coat that is sprayed with sufficient velocity, impact and heating of the sprayed particles to promote migration of such particles into said tears, folds and undercuts for mechanical interlocking with said honed surface as well as chemical metallurgical interaction with said prepared surface through said residue;
• and (e) thermally spraying a top coat onto said bond coat which has increased wear resistance and has lubricity.