Method for chemically plating double-layer Ni-P plating layer

Abstract

The invention relates to a method for chemically plating a double-layer Ni-P plating layer on different matrixes. The method comprises the following steps of: (1) chemical oil removal: removing oil of a workpiece in oil removal liquid; (2) first activation: activating in sulfuric acid with volume fraction of 5-10%; (3) chemically plating an acid high-phosphorus Ni-P layer; (4) second activation: activating in sulfuric acid with volume fraction of 10%; (5) chemically plating an acid low-phosphorus Ni-P layer; and (6) carrying out treatment after plating. In the invention, the workpiece is chemically plated with the acid high-phosphorus Ni-P layer which is then plated with the acid low-phosphorus Ni-P layer; the plating layer has the advantages of good binding force, good uniformity and density, high hardness, corrosion resistance and strong wear resistance; the low-phosphorus and high-phosphorus chemical plating Ni-P liquid does not contain toxic heavy metal elements such as lead, cadmium, hexavalent chromium and the like, thus the harm to the environment and human bodies is reduced, and the liquid is environment-friendly plating liquid; and meanwhile, the wastewater is easy to treat at low cost, and the life cycle of the plating liquid is long.

Description

Technical field

[0001] The invention relates to a method for electroless Ni-P plating, in particular to a method for electroless plating a double-layer Ni-P coating. Background technique

[0002] The electroless amorphous nickel-phosphorus (Ni-P) alloy coating has excellent resistance to NaCl, H 2 S and CO 2 Corrosion performance and good wear resistance. At present, single-layer electroless Ni-P plating is mostly used. The single-layer Ni-P alloy electroless plating layer is a closed protective layer (ie cathodic protective layer) for steel materials, and only when the plating layer is absolutely intact (ie no porosity) It plays a protective role. If there are defects such as pores, the plating layer and the matrix in the defect will form a corrosion cell and be corroded. Due to the small area of ​​the matrix at the pores and the high current density, the coating will not only have no protective effect on the matrix at this time, but will accelerate its corrosion. At present,...