阅读说明：本技术 电镀锌黑变控制方法 (Electrogalvanizing blackening control method ) 是由 李冬 徐晶 姜波 于 2019-11-08 设计创作，主要内容包括：本发明涉及一种电镀锌黑变控制方法,其包括除油、热水洗、除锈、冷水洗、去离子水洗、镀锌、烘干及贮存步骤。本发明不仅确定了电镀锌黑变控制措施,更提高了镀锌层对产品的防护质量,对于电镀锌层的研究具有十分重要的价值。(The invention relates to a blackening control method for electrogalvanizing, which comprises the steps of oil removal, hot water washing, rust removal, cold water washing, deionized water washing, galvanizing, drying and storage. The invention not only determines the blackening control measures of the electrogalvanizing, but also improves the protection quality of the galvanized layer to the product, and has very important value for the research of the electrogalvanizing layer.)

1. The method for controlling blackening of the electrogalvanizing is characterized by comprising the following steps:

step 1, deoiling: soaking the workpiece in gasoline or industrial alcohol at normal temperature for 5-10min to remove oil stain on the surface; then electrolytic degreasing is carried out;

step 2, hot water washing: cleaning the surface of the workpiece for 30-60s by using hot water at the temperature of 90-100 ℃, and removing alkali liquor and salt liquor remained on the surface of the workpiece;

step 3, derusting: derusting the surface of the workpiece by using a derusting liquid;

step 4, cold water washing: performing countercurrent rinsing with flowing cold water at 15-20 deg.C for 30-60 s;

step 5, washing with deionized water: cleaning the workpiece for 30-60s in an environment of 15-30 ℃ by using deionized water before the workpiece enters a galvanizing bath, and ensuring that no other ions enter the galvanizing bath on the surface of the workpiece;

step 6, galvanization: using ZnSO4.7H2O 450g/L as main salt, using sulfuric acid with mass concentration of 98% as pH regulator to carry out electroplating, wherein the electroplating temperature is 30-60 ℃, the electroplating time is 3-4 min, the electroplating pH value is 1.8-2.0, the electrode plates are graphite and lead plates, the thickness of a zinc layer is 10-12 mu, and the current density is 15A/dm ²；

And 7, drying: drying the galvanized workpiece for 10min at the temperature of 80-90 ℃;

and 8, storing: the galvanized workpieces were stored at relative humidity: 0-65% and relative temperature of 0-30 deg.C.

2. The method for controlling blackening of electrogalvanizing according to claim 1, wherein in the step 1, the electrolyte in the electrolytic degreasing is prepared from 20-50g/L of sodium hydroxide, 30-50g/L of sodium carbonate, 20-30g/L of sodium phosphate and 3-5g/L of sodium silicate; the electrolytic oil removal time is 10-20min, and the current density is 5-10A/dm ²The temperature is 60-90 ℃, and the polar plate material is steel plate or nickel plate; the mass concentration of the industrial alcohol is 90 percent.

3. The method as claimed in claim 1, wherein in step 3, the rust removing solution is prepared from hydrochloric acid 250-300g/L and chlordine 3-5g/L, the rust removing time is 0.5-3min, and the rust removing temperature is normal temperature.

Technical Field

The invention relates to a blackening control method for electrogalvanizing.

Background

After the electrogalvanizing is stored for a period of time under the environment condition of high temperature and high humidity, the phenomenon that a layer of delicate, continuous and slightly metallic black or dark brown film layer is generated on the surface is the blackening phenomenon of the electrogalvanizing. The blackening phenomenon is essentially an initial corrosion phenomenon, and is caused by the formation of interstitial corrosion products of under-oxidized zinc oxide in a high-temperature and high-humidity environment of the outermost layer of zinc; it seriously affects the appearance of the product and reduces the bonding force with the painted layer.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for controlling blackening of electrogalvanizing, which solves the problem of blackening of galvanized steel and improves the corrosion resistance of the galvanized steel.

The technical scheme of the invention comprises the following steps:

step 1, deoiling: soaking the workpiece in gasoline or industrial alcohol at normal temperature for 5-10min to remove oil stain on the surface; then electrolytic degreasing is carried out;

step 2, hot water washing: cleaning the surface of the workpiece for 30-60s by using hot water at the temperature of 90-100 ℃, and removing alkali liquor and salt liquor remained on the surface of the workpiece;

step 3, derusting: derusting the surface of the workpiece by using a derusting liquid;

step 4, cold water washing: performing countercurrent rinsing with flowing cold water at 15-20 deg.C for 30-60 s;

step 5, washing with deionized water: cleaning the workpiece for 30-60s in an environment of 15-30 ℃ by using deionized water before the workpiece enters a galvanizing bath, and ensuring that no other ions enter the galvanizing bath on the surface of the workpiece;

step 6, galvanization: electroplating by using ZnSO 4.7H 2O 450g/L as main salt and sulfuric acid with the mass concentration of 98% as a pH regulator at the electroplating temperature of 30-60 ℃ for 3-4 min at the electroplating pH value of 1.8-2.0, wherein the electrode plates are graphite and lead plates, the thickness of a zinc layer is 10-12 mu, and the current density is 15A/dm ²；

And 7, drying: drying the galvanized workpiece for 10min at the temperature of 80-90 ℃;

and 8, storing: the galvanized workpieces were stored at relative humidity: 0-65% and relative temperature of 0-30 deg.C.

In the step 1, the electrolyte in the electrolytic degreasing is prepared from 20-50g/L of sodium hydroxide, 30-50g/L of sodium carbonate, 20-30g/L of sodium phosphate and 3-5g/L of sodium silicate; the electrolytic oil removal time is 10-20min, and the current density is 5-10A/dm ²The temperature is 60-90 ℃, and the polar plate material is steel plate or nickel plate; the mass concentration of the industrial alcohol is 90 percent.

In the step 3, the rust removing liquid is prepared from 300g/L hydrochloric acid 250-5 g/L and 3-5g/L rhodanide, the rust removing time is 0.5-3min, and the rust removing temperature is normal temperature.

The invention has the following positive effects:

the method not only determines the blackening control measures of the electrogalvanizing, but also improves the protection quality of the galvanized layer on the product, and has very important value for the research of the electrogalvanizing layer.

Drawings

FIG. 1 is a flow chart of the electrogalvanizing process of the present invention.

FIG. 2 is a graph showing the change of the thickness of the plating layer with the current density.

FIG. 3 is a graph showing the change of the thickness of the plating layer according to the concentration of the main salt.

FIG. 4 is a graph showing the change of the thickness of the plating layer with the plating time.

FIG. 5 is a graph showing the change of the thickness of the plated layer with temperature.

Fig. 6a is a metallographic photograph of the plating layer with the bath pH 1.6.

Fig. 6b is a metallographic photograph of the plating solution with pH 1.8.

Fig. 6c is a metallographic photograph of the plating layer when the pH of the plating solution was 2.0.

Fig. 6d is a metallographic photograph of the plating solution with pH 2.1.

Fig. 6e is a metallographic photograph of the plating solution with pH 2.4.

FIG. 7 is a graph of a blackening time curve.

FIG. 8 is a graph showing a black change and a current density change.

FIG. 9 is a graph showing humidity and blackening curves.

FIG. 10 is a graph showing the temperature and blackening curves.

Detailed Description