CN102888601A

CN102888601A - Trivalent chromium black passivation plating solution for zinc coating

Info

Publication number: CN102888601A
Application number: CN2012104160640A
Authority: CN
Inventors: 陈大弟
Original assignee: NANJING DADI REFRIGERATION FOOD CO Ltd
Current assignee: NANJING DADI REFRIGERATION FOOD CO Ltd
Priority date: 2012-10-26
Filing date: 2012-10-26
Publication date: 2013-01-23

Abstract

The invention discloses trivalent chromium black passivation plating solution for a zinc coating, comprising the following components by mass fraction: 0.1-0.3mol/L of trivalent chromium salt, 10-50g/L of complexant, 0.2-1g/L of cobaltous sulphate, 2-5g/L of nickel sulphate, 0.5-2g/L of potassium sulfocyanide, 10-20g/L of phosphoric acid and 2-6ml/L of methanoic acid. A black passivation layer obtained by the invention is uniform and black on the surface, does not grow dim, can pass a 72-hour neutral salt spray test and has high anti-corrosion property.

Description

A kind of zinc coating trivalent chromium is deceived blunt plating bath

Technical field

The invention belongs to the electroplating chemical technical field, relate in particular to the zinc coating trivalent chromium black passivation solution.

Background technology

Workpiece zinc-plated complete after, usually to do Passivation Treatment.At present for the environmental protection purpose, sexavalent chrome black inactivation process originally all is modified into the trivalent chromium black passivation technology, but also there is the shortcoming of several respects in existing trivalent chromium passivation process: 1, the erosion resistance not as the sexavalent chrome black passivation solution is good, and general neutral salt spray test can only reach 48～72h; 2, common trivalent chromium black passivation layer is inhomogeneous, sends out easily color; 3, bonding force is inadequate, has show-through impression after the bending.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides the black blunt plating bath of a kind of zinc coating trivalent chromium, the black passivation layer surface uniform of deposition, bonding force is good, and neutral salt spray test can reach more than the 72h.

Technical scheme: for solving the problems of the technologies described above, the present invention by the following technical solutions: a kind of zinc coating trivalent chromium is deceived blunt plating bath, comprises the component of following massfraction:

Chromic salt 0.1～0.3mol/L;

Coordination agent 10～50g/L;

Rose vitriol 0.2～1g/L;

Single nickel salt 2～5g/L;

Potassium sulfocyanate 0.5～2g/L;

Phosphatase 11 0～20g/L;

Formic acid 2～6ml/L.

As preferably, described coordination agent is one or more the mixture in Citrate trianion, xitix, EDTA, thiocarbamide, the ammonium oxalate.

As preferably, described chromic salt is chromium nitrate, chromium sulphate or chromium chloride.

As preferably, each component concentration is as follows: chromium nitrate 0.15mol/L, rose vitriol 0.6g/L, single nickel salt 2.5g/L, potassium sulfocyanate 1g/L, phosphatase 11 2g/L, formic acid 3.5ml/L, wherein coordination agent is the mixture of the thiocarbamide of the EDTA of 20g/L ammonium oxalate, 10g/L and 2g/L.

Beneficial effect: compared with prior art, the present invention has the following advantages: the black passivation layer surface that obtains is even black, do not grow dim, and can pass through the 72h neutral salt spray test, has high Corrosion Protection.

Embodiment

The below is further described the present invention.

Add an amount of pure water in plating tank, add the phosphoric acid of 12g/L and the formic acid of 3.5ml/L and stir, then add the mixture of the thiocarbamide of the EDTA of 20g/L ammonium oxalate, 10g/L and 2g/L, stirring fully, dissolving obtains out cylinder liquid.To dissolve respectively with pure water in addition and obtain chromium nitrate solution, cobalt sulfate solution and nickel sulfate solution, join successively above-mentioned obtaining out in the cylinder liquid, chromium nitrate 0.15mol/L wherein, rose vitriol 0.6g/L, single nickel salt 2.5g/L, and to adjust pH with phosphoric acid or sodium hydroxide solution be 2.0～3.0.

After having plated the activated washing of workpiece of zinc, enter and keep 30～60s to obtain evenly coming off through bending 3 times, having no without the black coating that grows dim in the above-mentioned trivalent chromium black passivation solution.Through neutral salt spray test NSS, can reach the above grading of 72h more than 9.

Claims

1. a zinc coating trivalent chromium is deceived blunt plating bath, it is characterized in that comprising the component of following massfraction:

Chromic salt 0.1～0.3mol/L;

Coordination agent 10～50g/L;

Rose vitriol 0.2～1g/L;

Single nickel salt 2～5g/L;

Potassium sulfocyanate 0.5～2g/L;

Phosphatase 11 0～20g/L;

Formic acid 2～6ml/L.

2. the black blunt plating bath of described zinc coating trivalent chromium according to claim 1 is characterized in that: described coordination agent is one or more the mixture in Citrate trianion, xitix, EDTA, thiocarbamide, the ammonium oxalate.

3. described zinc coating trivalent chromium is deceived blunt plating bath according to claim 1, and it is characterized in that: described chromic salt is chromium nitrate, chromium sulphate or chromium chloride.

4. described zinc coating trivalent chromium is deceived blunt plating bath according to claim 1, it is characterized in that each component concentration is as follows: chromium nitrate 0.15mol/L, rose vitriol 0.6g/L, single nickel salt 2.5g/L, potassium sulfocyanate 1g/L, phosphatase 11 2g/L, formic acid 3.5ml/L, wherein coordination agent is the mixture of the thiocarbamide of the EDTA of 20g/L ammonium oxalate, 10g/L and 2g/L.