JPS59170294A - Pretreatment before plating - Google Patents

Abstract

PURPOSE:To obtain polished metallic parts having plating which has high flatness and does not cause stripping by carrying out a chemical polishing stage between a rust removing stage and a plating stage when the polished surfaces of metallic parts are plated. CONSTITUTION:When the polished surfaces of polished metallic parts are plated with hard chromium, the surfaces are degreased, washed, and derusted. The pretreated surfaces are chemically polished, activated, washed, and plated with chromium. The chemical polishing is carried out with a mixed soln. contg. about 25g/l oxalic acid, about 15g/l hydrogen peroxide and about 1g/l sulfuric acid, and very small metallic chips present on the surfaces to be plated are removed by the polishing to make the surfaces flat.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a plating pretreatment method, particularly to a method effective for chromium plating on the polished surface of US-processed metal parts.

(b) Background of the Technology Generally speaking, the plating pretreatment process that is carried out is in the order of degreasing, washing with water, rust, activation, washing with water, and polishing.

The type of plating is selected depending on the purpose, but hard chrome plating is performed to improve the wear resistance of the material.

fcl Conventional technology and problems However, for precision metal parts where the object to be plated has been polished, there is a problem that the above-mentioned general-purpose plating pretreatment method has poor surface flatness, which is fatal for the parts that require precision. It becomes a defect. Note that such defective plated parts are subjected to the same plating treatment again after the plating is peeled off.

The inventors of the present invention investigated this problem and found that the machined surface of such parts was scattered with tiny metal chips that were invisible to the naked eye and whose origin was unknown, whether they had separated from the polishing equipment or had come flying from somewhere else. It was found that the plating applied to the plate impeded the flatness. Moreover, this raised plated part has the disadvantage that it is more likely to peel off than other parts.

(dl) Purpose of the Invention In view of the above-mentioned conventional situation, it is an object of the present invention to provide a method for plating polished metal parts while maintaining excellent flatness.

tel Structure of the Invention In order to achieve the above object, the present invention is characterized in that when plating the polished surface of a polished metal component, a chemical polishing process is inserted after the rust removal process and before the metal polishing process. A plating pretreatment method is proposed.

ff) Embodiments of the Invention An embodiment in which the present invention is applied to hard chrome plating will be described in detail below. That is, the hard chromium plating pretreatment method for polished metal parts according to the present invention generally includes the following steps: degreasing, washing with water, removing rust, removing dirt, activating, washing with water, and chromium plating. In short, according to the characteristics of this embodiment, chemical polishing was performed between the derusting process and the activation process using 25g/j of oxalic acid as shown by filling in the Anglines.
2. Hydrogen peroxide 15g/β and sulfur flJ, Ig
/I! This is done using a polishing liquid made from a mixture of , and the minute metal chips scattered on the surface to be plated of a polished metal part are removed without losing the surface condition of the material of the part.

Thereafter, hard chrome plating is applied to the flattened surface to be plated.

fg) According to the plating pretreatment method of the present invention described in detail, polished metal parts with very good plating flatness (and no peeling of the plating) can be obtained.

Claims (2)

[Claims] (1) A plating pretreatment method characterized by inserting a chemical polishing process after the rust removal process and before the polishing process when plating the polished surface of a polished metal part. (2) The plating pretreatment method according to claim 11, wherein the plating is hard chrome plating.