Method of treating light metal cylinder bore walls to receive thermal sprayed metal coatings
Reference Number: N 01-02
Inventors: Palazzolo, Christopher K.; Nageswar Rao, V. Durga; Shepley, Barry E.
The invention, meeting the above object, is 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 oxide by use of spiral overlapping cross-abrasions having certain peaks and valleys of said 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 agent that produces a protective 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 said residue; and (d) thermally spraying a metallic bond coat on said honed and washed surface to render a adhesion between said coating and prepared surface that is at least 2800 psi.
The washing solution preferably contains an aluminate forming agent that consists of sodium xanthate hydroxide or meta silicate, which may be fluoro siliconized; the alkalinity agent may comprise anionic hydroxides or meta silicates of sodium or potassium; the surfactants may comprise nonionic fluoronated hydrocarbons such as Fluorad.RTM. produced by 3M company, and the solutions may comprise non-soaping and non smutting agents such as octoates of sodium and potassium, and hydrocarbons such as sodium gluconate.