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Electrochemical method of forming black trivalence chromic oxide coating and black trivalence chromic oxide coating

A chromium oxide and electrochemical technology, applied in the field of electrochemistry for forming black trivalent chromium oxide coating and its black trivalent chromium oxide coating, can solve the problems of inability to form blackening degree and low blackening degree, and reduce waste water Difficulty in handling, enhancement of mechanical properties, effect of stress relief

Active Publication Date: 2014-01-15
DEXNANO CHEM TECH
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Problems solved by technology

At present, more and more researchers have invested in the research of trivalent chromium electroplating, hoping to replace the highly polluting hexavalent chromium, while maintaining the excellent characteristics of the chromium electroplating layer, which is an active development direction for the industry, such as, U.S. Patent Publication No. US20100155256 or as Wang Yuqin (Yu-Qin Wang) and Cao Shuhong (Shu-Hong Cao) in Electroplating and Environmental Protection Journal, Volume 25, No. 3, 2005, proposed "Formic acid-methanol-urea system trivalent chromium plating process ( A Study of Formic Acid-Methanol-Urea Trivalent Chromium Plating System) "The electroplating method of trivalent chromium solution with formic acid-methanol-urea as additive can improve the burning phenomenon of trivalent chromium electroplating chromium plating layer and can gradually replace Electroplating of hexavalent chromium; another example is Taiwan Patent Publication No. TW200911699, which uses alkaline trivalent chromium electroplating to form a chromium hydroxide electroplating layer, and Chinese Patent Application No. CN200710086887.0 or CN200610019033.6 uses chromium sulfate, sodium sulfate, boric acid, sulfuric acid Aluminum, sodium lauryl sulfate, complexing agent, stabilizer, etc. form a trivalent chromium electroplating solution with a full sulfate system, but it is still unable to form an electroplating layer with high blackening degree, corrosion resistance, high hardness and high wear resistance
[0005] In addition, in terms of chromium electroplating, especially the chromium oxide of trivalent chromium electroplating: the early US patent US4196063 has disclosed the use of trivalent chromium ions, iron ions, cobalt ions and phosphate radicals to electroplate a black trivalent chromium electroplating chromium layer, but The degree of blackening is not high

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  • Electrochemical method of forming black trivalence chromic oxide coating and black trivalence chromic oxide coating
  • Electrochemical method of forming black trivalence chromic oxide coating and black trivalence chromic oxide coating

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Embodiment 1

[0074] Please see Figure 4 , Which is the surface topography of the black trivalent chromium oxide plating layer 3 of this embodiment. The trivalent chromium electroplating solution 4 used in this embodiment is a sulfate electroplating bath, and its composition and operating conditions are shown in Table 2. The black trivalent chromium oxide plating layer 3 formed by electroplating using this trivalent chromium electroplating solution 4 and operating conditions is as follows Table three. The trivalent chromium electroplating bath 4 is a sulfate electroplating bath, the blackening agent 6 is fluorosilicic acid, the co-deposition agent 7 is cobalt sulfate, the complexing agent 9 is sodium hypophosphite, and the iron material is used as the substrate 1. Density 10A / dm 2 The operating temperature is 25° C., and the operating time is 1 minute; the resulting black trivalent chromium oxide coating 3 has a blackening degree of about 42.7% as measured by a Spectra Scan Colorimeter (Spe...

Embodiment 2

[0081] The trivalent chromium electroplating solution 4 used in this embodiment is a sulfate electroplating bath, and its composition and operating conditions are shown in Table 4. The black trivalent chromium oxide plating layer 3 formed by electroplating using this trivalent chromium electroplating solution 4 and operating conditions is as follows Table five. The trivalent chromium electroplating solution 4 is a sulfate electroplating bath, the blackening agent 6 is nitric acid, the co-deposition agent 7 is cobalt nitrate, the complexing agent 9 is sodium hypophosphite, and the copper alloy is used as the substrate 1, and the current density is used during electroplating. 30A / dm 2 The operating temperature is 10°C, and the operating time is 3 minutes; the resulting black trivalent chromium oxide coating 3 has a gray scale value of about 30.1%, roughness of about 0.8μm, and a coefficient of friction of about 0.4237. The electroplated layer of the embodiment is not subjected to...

Embodiment 3

[0088] The trivalent chromium electroplating solution 4 used in this embodiment is a sulfate electroplating bath, and its composition and operating conditions are shown in Table 6. The black trivalent chromium oxide plating layer 3 formed by electroplating using this trivalent chromium electroplating solution 4 and operating conditions is as follows Table seven. The trivalent chromium electroplating bath 4 is a sulfate electroplating bath, the blackening agent 6 is potassium nitrate, the co-deposition agent 7 is cobalt nitrate, the complexing agent 9 is sodium hypophosphite, the stainless steel is used as the substrate 1, and the current density is used during electroplating. 50A / dm 2 The operating temperature is 0℃, and the operating time is 5 minutes; the resulting black trivalent chromium oxide coating 3 has a gray scale value of about 27.3% and a roughness of about 0.5μm. The friction coefficient is about 0.3237, the electroplating layer of this embodiment is not subjected ...

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Abstract

The invention discloses an electrochemical method of forming black trivalence chromic oxide coating and the black trivalence chromic oxide coating; a black trivalence chromic oxide electroplating layer is formed on the surface of the substrate through the electroplating method; black trivalence chromic oxide electroplating liquid comprises chromic salt, darkening agent containing nitrate, co-deposition agent containing cobalt salt, complexing agent of inorganic salt, and water solution formed by PH modifier of inorganic acid salt. The thickness of the black trivalence chromic oxide electroplating layer formed under the set electroplating operation condition is between 0.5-15 micrometers, the gray-scale value of the darkening degree is below 45%, and the requirements of corrosion resistance, high surface hardness and good wear resistance are satisfied so as to be applied on tools needing high precision, high hardness and wear resistant property, such as a slide rail and a screw rod.

Description

Technical field [0001] The invention relates to an electrochemical method for forming a black trivalent chromium oxide coating and the electrochemical method is used to form a black trivalent chromium oxide coating on a conductive substrate by electroplating, so that it has a high degree of blackening, corrosion resistance, With high hardness and high wear resistance, it can be applied to tools with high load requirements such as slide rails and screws of the machine tool. Background technique [0002] In order to increase the hardness, wear resistance, corrosion resistance and decoration of the metal surface, the use of chromium electroplating or chromated chemical conversion coating has become a common technology. Generally, chromium electroplating or hard chromium electroplating mainly uses chromium. Acid (hexavalent chromium, Cr 6+ ), but hexavalent chromium chromic acid is very toxic (about 100 times more than trivalent chromium) and is a very serious carcinogen. The waste w...

Claims

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Application Information

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IPC IPC(8): C25D3/06C25D3/08
Inventor 葛明德白清源吕承恩吴亚竹吴柏范
Owner DEXNANO CHEM TECH
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