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Electrodeposition of chromium from trivalent chromium using modulated electric fields

a trivalent chromium and electric field technology, applied in the field of electroplating of chromium metal from a trivalent chromium electroplating bath, can solve the problems of worker exposure to hexavalent chromium, and achieve the effect of improving the visual uniformity and density of the coating

Inactive Publication Date: 2013-08-29
FARADAY TECH INC
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  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent text describes a method for producing dense and scalable hard chrome coatings using a trivalent chromium plating bath. By controlling the electric field during electrodeposition, the process produces coatings that are as hard and wear-resistant as conventional hexavalent chromium baths. The method also involves reversing the polarity of the substrate and inter interrupting or varying the electric field during the electrodeposition process to improve coating uniformity. The developed process produces chrome coatings that are visually uniform and have high hardness values.

Problems solved by technology

One problem associated with this type of coating process is worker exposure to the hexavalent chromium during plating, which is overcome by replacing the carcinogenic material with a benign trivalent chromium plating electrolyte.

Method used

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  • Electrodeposition of chromium from trivalent chromium using modulated electric fields
  • Electrodeposition of chromium from trivalent chromium using modulated electric fields
  • Electrodeposition of chromium from trivalent chromium using modulated electric fields

Examples

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examples

[0041]The present invention will be illustrated by the following examples, which are intended to be illustrative and not limiting.

[0042]A visually uniform and scalable coating can be formed the inner diameter of 4130 steel pipes, used din the landing gear of aircrafts. A dimensionally stable anode (DSA) was used as the counter electrode. The electrodeposition process parameters used to deposit a visually uniform coating consisted forward only pulse waveform with a forward duty cycle of at least 80% and a frequency of at least 500 Hz at the applied forward current density between 25 and 45 A / dm2. The nominal electrolyte bath temperature was between 90 and 150° F. and electrolyte flow rate held constant throughout the deposition process.

[0043]FIG. 2 and FIG. 3 demonstrate the microstructure of the coatings obtained during deposition the process. These cross-sections show a dense coating with few microcracks, which are advantageous for the production of a wear resistant chrome coating....

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Abstract

A layer of chromium metal is electroplated from trivalent chromium onto an electrically conducting substrate by immersing the substrate and a counter electrode in a electroplating bath and passing a modulated electric current between the electrodes. In one embodiment, the current contains pulses that are cathodic with respect to said substrate and in another embodiment the current contains pulses that are cathodic and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle greater than about 80%.

Description

GOVERNMENT RIGHTS[0001]The experimental work leading to this invention was funded in part by EPA Phase I SBIR program. Contract No. EP-D-11-044. The U.S. Government may have certain rights in the invention.FIELD OF THE INVENTION[0002]This invention relates to electrodeposition of chromium metal and more particularly to electrodeposition of chromium metal from a trivalent chromium electroplating bath as contrasted with conventional carcinogenic hexavalent chromium electroplating bath.BACKGROUND[0003]The US Environmental Protection Agency identified hexavalent chromium as one of 17 “high-priority” toxic chemicals based on their known health and environmental effects, production volume, and potential for work exposure. Typical thick, hard chrome coatings have been produced from a hexavalent chromium bath using a direct current deposition process. One problem associated with this type of coating process is worker exposure to the hexavalent chromium during plating, which is overcome by r...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C25D5/18C25D3/10C25D3/06
CPCC25D5/18C25D3/10C25D3/06C25D5/627C25D5/625C25D5/617C25D5/611
Inventor HALL, TIMOTHYKAGAJWALA, BURHANUDDIN
Owner FARADAY TECH INC
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