Electroplating and chemical plating combined plating solution used for zinc die cast alloy

Abstract

The invention discloses an electroplating and chemical plating combined plating solution used for zinc die cast alloy. The combined plating solution comprises a cyanide-free pre-electroplated copper electroplating solution and a chemical nickel-plating electroplating solution. The cyanide-free pre-electroplated copper electroplating solution comprises 100-120 g / L of cupric pyrophosphate, 40-50 g / L of sodium pyrophosphate, 280-300 g / L of trisodium citrate, 26-30 g / L of sodium potassium tartrate tetrahydrate, 30-50 g / L of HEDP, 260-280 g / L of ethidene diamine, 2-3 g / L of ammonium hydrogen difluoride, 2-3 g / L of sodium fluoride and 6-8 g / L of lithium fluoride, wherein the pH value of ammonium hydroxide is adjusted to be 8.5-9.5. The chemical nickel-plating electroplating solution comprises 30-40 g / L of NiSO4.6H2O, 2-4 g / L of C6H8O7.H2O, 3-5 g / L of lactic acid, 0.5-1.5 g / L of propionic acid, 16-20 mL / L of HF(40%), 14-16 g / L of NH4HF2, 14-16 g / L of NaH2PO2.H2O, 20-22 mL / L of NH3.H2O and 2-4 mg / L of thiourea, and the pH value is 4.5-5.5. The two electroplating solutions are matched and stored independently, during using, the cyanide-free pre-electroplated copper electroplating solution is used for carrying out cyanide-free electroplated copper bottoming firstly, and then the chemical nickel-plating electroplating solution is used for carrying out chemical nickel plating.

Description

technical field [0001] The invention relates to the field of surface treatment, in particular to a combined electroplating and electroless plating bath for die-casting zinc alloys. Background technique [0002] Due to its cheap price, low melting point, and especially good die-casting process performance, zinc alloy has been widely used in the manufacture of small hardware accessories, and can also be used to manufacture decorative and practical metal parts. Such as various zippers, belt buckles, luggage accessories, car nameplates and military badges, etc. [0003] The appearance of zinc alloy die castings is gray and white, and there are various defects on the surface, such as: slag inclusions, shrinkage cavities, etc. Therefore, without surface treatment, its usability and decoration are very poor. A common surface treatment method is electroplating. According to the different decorative and functional requirements, there are certain differences in the electroplating pr...

AI Technical Summary

Problems solved by technology

[0006] Neutral nickel pre-plating is mainly used for the rack plating process of zinc alloy die castings, and the main component of the plating solution is NiSO 4 , sodium citrate, etc., do not contain cyanide, but the bonding force between the nickel plating layer and the substrate is far inferior to the performance of cyanide copper plating pre-plating, and the product qualification rate is low

Moreover, due to the poor activation ability of the neutral nickel plating solution on zinc alloy die castings, there are higher requirements for its pretreatment

The neutral nickel plating process generally cannot be used for barrel plating of zinc alloy die castings, therefore, the range of industrial applications is not very wide

In addition, the cost of neutral nickel plating solution is high, and wastewater treatment is difficult, which limits its large-scale application in industry.

[0007] Other zinc alloy die casting pre-plating processes include chemical copper plating, HEDP copper plating, copper-tin alloy electroplating, etc., all of which have not been practically applied in industry due to problems such as bonding force, cost, and wastewater treatment.