Claims:We claim:
1. A method for anti-tarnish non-cyanide based silver plating, comprising the steps of:
preparing an electrolytic solution (101);
preparing a surface substrate (102);
preparing pure silver (103);
transferring the surface substrate (102) and the anode (103) into the electrolytic solution (101) for plating to produce a silver plated substrate;
removing the silver plated substrate from the electrolytic solution after a predefined time,
characterized in that
the electrolytic solution is prepared using the mixture of Succinimide, Silver Nitrate, Methanesulfonic acid, Potassium Carbonate and Diethylenetriamine.
2. The method as claimed in claim 1, wherein the material of the surface substrate (102) is preferably copper substrate.
3. The method as claimed in claim 1, wherein the surface preparation of copper substrate (102) consists of mechanical cleaning and chemical cleaning.
4. The method as claimed in claim 1, wherein the pH of the electrolytic bath solution is maintained at a range of 9.5-10.0 by mixing Potassium Hydroxide.
5. The method as claimed in claim 1, wherein pure silver (103) acts as anode.
6. The method as claimed in claim 1, wherein the silver striking is done at 1.5 Volt and for the predefined time approximately at 30 seconds.
7. The method as claimed in claim 1, wherein the silver plating is done at a voltage range of 0.6-0.8V.
8. The method as claimed in claim 1, wherein time of silver plating varies from 15 to 30 minutes.
9. The method as claimed in claim 1, wherein the thickness of the silver plated substrate is in the range of 15-20 microns.
10. The method as claimed in claim 1, wherein the color of the silver plating substrate is bright yellowish.
, Description:ANTI-TARNISH NON-CYANIDE BASED SILVER PLATING
TECHNICAL FIELD
[0001] This present invention relates to the field of Electroplating. More particularly, the present invention relates to developing an Anti-Tarnish Non-cyanide based Silver Plating process on copper plates/components which generates a bright and adherent layer of silver
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention.
[0003] Electroplating, also known as electrodeposition is the process of coating a metal object with another metal, using an electrical current passed through a chemical solution. Through ceaseless advancement in technology and in-depth understanding of electrochemistry, it became a common and integral part of industrial processes serving varied purpose. Generally, electroplating is applied for decorative coating, corrosion protection, special surface properties, mechanical and electrical properties. Silver was among the first electroplated metals as it was first discovered to be soluble in cyanide. Since then and now, majority of commercial silver plating solutions are cyanide based. This has been the case due to its numerous advantages like cyanide is an excellent complexing agent making it more tolerant to metal contamination and it can guarantee a pure white and bright deposit which are desired by customers.
[0004] As shown in fig. 1, this system comprises a cathode 101 (the material to be plated/substrate), an anode 102 (the plating metal or inert conductor), an electrolytic solution 103 (a salt solution used to immerse the anode and cathode containing metal ions to be coated) an electrical current provided by an electrical source 104 such as a battery or other power unit.
[0005] This process results in a thin layer of metal being deposited onto the surface of a work piece called the substrate. In this process, Target is connected to Anode and Substrate is connected to Cathode and are dipped in an electrolytic solution. The process used for silver deposition on substrate is known as Silver Electroplating.
[0006] Technical problem: Most commonly used chemicals for preparing silver plating electrolyte is potassium cyanide because of its high throughput. In India large number of plating industries uses potassium cyanide/sodium cyanide for silver plating of various components including its aesthetic uses like jewelry applications. However, there are many health and environmental hazards involved with cyanide based silver plating. If not treated properly, disposed waste from plating industry can contaminate the underground and river water of the area which comes in its contact. As the awareness towards these hazards is increasing, law and regulations are being formed by the government for the cyanide usage in silver plating. In this situation, it is obvious that industrial silver plating business may get hampered badly in the near future if sustainable alternative to cyanide based silver plating is not developed immediately.
[0007] Technical Solution: Accordingly, there is a need to develop silver plating on copper substrate using Non-cyanide based electrolyte.

OBJECTS OF THE DISCLOSURE
[0008] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0009] It is a general object of the present disclosure is to provide a method of Non-cyanide based silver plating on copper substrate where main complexing agent was Sodium Thiosuphate.
[0010] It is another object of the present disclosure is to develop a non-cyanide based silver plating method which has better adhesion and anti-tarnish property.
[0011] It is another object of the present disclosure is to generate high quality, adherent and bright silver plating.
[0012] It is another object of the present disclosure is to provide a method that is environment friendly.
[0013] It is another object of the present disclosure is to provide a method of cyanide based silver coating that does not impose any health hazards to the operator working in the industry.
[0014] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY
[0015] This summary is provided to introduce concepts related to a method for Non-cyanide based silver electroplating. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0016] In an embodiment, the present disclosure relates to a method for Non-cyanide based silver electroplating on copper substrate and its anti-tarnish treatment. Electrolytic solution is based on Succinimide, Silver Nitrate, Methanesulphonic Acid, Potassium Carbonate and diethylene triamine. All these chemicals are dissolved in demineralized water to prepare the electrolytic solution. Later Diethylenetriamine is mixed in the solution as anti-tarnish agent. Once electrolyte is ready, surface preparation of the copper plates is done by grinding it with sand paper followed by chemical cleaning and acid pickling. Silver plate (Anode) and copper plate (Cathode) were dipped inside the electrolyte. A rectifier was then used to supply the DC current through anode, cathode and electrolyte. After 30 minutes of plating, copper substrate is removed from the electrolyte and rinsed by Demineralized water.
[0017] In an aspect, the the material of the surface substrate is preferably copper.
[0018] In an aspect, the surface preparation of copper substrate consists of mechanical cleaning and chemical cleaning
[0019] In an aspect, the driven gear and the the pH of the electrolytic bath solution is maintained at a range of 9.5-10.0 by mixing Potassium Hydroxide.
[0020] In an aspect, teeth ratio in between the silver striking is done at 1.5 Volt and for the predefined time approximately at approximately 30 seconds.
[0021] In aspect, the first pin defines the the silver plating is done at a voltage range of 0.6-0.8V.
[0022] In an aspect, the time of silver plating varies from 15 to 30 minutes.
[0023] In an aspect, the thickness of the silver plated substrate is in the range of 15-20 microns.
[0024] In an aspect, the silver plated substrate is tested for 3 cycles of 90-degree bend test for checking adhesion of the coating on copper substrate.
[0025] In an aspect, the color of the silver plating substrate is yellowish bright.
[0026] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0027] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0028] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0030] FIG. 1 illustrate an existing electrolytic cell with the presence of anode, cathode, battery and electrolyte.
[0031] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter.
DETAILED DESCRIPTION
[0032] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0033] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0035] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0036] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0037] The present invention relates to a method of Non-cyanide based silver electroplating on copper substrate (102) which is has better adhesion and anti-tarnish property and is less hazardous. It comprises the steps of preparing an electrolytic solution (101) prepared with Succinimide, Silver Nitrate, Methanesulphonic Acid, Potassium Carbonate and diethylene triamine. All these chemicals are dissolved in demineralized water to prepare the electrolytic solution (101). Later Diethylenetriamine is mixed in the solution as anti-tarnish agent.
[0038] Along with that a copper substrate (102) is produced by means of physical and chemical cleaning. After that a Silver plate (Anode) and copper plate (Cathode) are dipped inside the electrolyte. A voltage striking is done followed by silver plating for 30 minutes at 0.7volts. After 30 minutes of plating, copper substrate (102) was removed from the electrolyte and rinsed by DM water.
[0039] The first step is preparing an electrolytic solution (101). Electrolyte bath comprises of the following chemicals
CHEMICAL QUANTITY
Silver Nitrate (AgNO3) 10-20gm/L
Methanesulfonic acid (CH4O3S) 30-40gm/L
Succinimide (C4H5NO2) 130-150gm/L
Potassium Carbonate (K2CO3) 15-30gm/L
Diethylenetriamine (C4H13N3) 1-5 ml/L
Potassium Hydroxide (KOH) to maintain pH ~ 10

[0040] Succinimide is first dissolved in demineralized water to a half of the electrolyte bath volume. Silver Nitrate and Methanesulfonic acid are then mixed together separately in demineralized water to one third of the electrolyte bath volume. Once Succinimide is dissolved, mixture of Silver Nitrate and Methanesulfonic acid is then mixed with the Succinimide solution. Potassium Carbonate and Diethylenetriamine is mixed slowly in the solution directly. The pH of the bath is measured and maintained in a range of 9.5-10.0 by adding Potassium Hydroxide.
[0041] The next step is to prepare copper surface substrate (102) for silver plating. Surface preparation can be categorized into two parts. The first one is mechanical cleaning. The mechanical cleaning of the substrate is done by grinding the substrate with sand paper to remove all the oxides. This process exposes and makes ready the substrate surface for chemical cleaning.
[0042] The second type of cleaning is chemical cleaning which is followed by mechanical cleaning. Substrate is first cleaned by organic solvent like Acetone for removal of any oily substance. The substrate is rinsed in demineralized water followed by acid pickling in 10% sulfuric acid (H2 SO4) for 10 seconds. At last the substrate is again rinsed in Demineralized water before silver plating.
[0043] The next step is transferring the copper surface substrate (102) for silver plating in the electrolytic solution (101). Here the copper surface substrate (102) act as a cathode and pure silver (103) dipped in the electrolytic solution (101) acts as an anode. Substrate is connected to the cathode and pure silver (103) is connected to the anode terminal of the rectifier (104). Both copper substrate (102) (Cathode) and Pure silver (103) (Anode) are dipped into the electrolyte bath before electroplating starts. After switching on the rectifier (104), striking is firstly done at 1.5V for approximately 30 Seconds followed by silver plating at 0.7V for 30 minutes to get the plating thickness of approximately 15 microns.
[0044] The last step is post plating treatment. After silver plating is done for at least 30 minutes, the substrate is removed from electrolyte bath and rinsed with demineralized water. It is then dried by compressed air. The obtained silver plating is bright in appearance and has a yellowish bright lustre.
[0045] A 3 cycles of 90-degree bend test is performed to check the adhesion of the plating. After the test it is found that, no crack or flaking is observed near the bent area. The thickness is measured through image analyser and is found to be in the range of 15-20 microns.
[0046] With the present method of non-cyanide based electroplating, the following technical advantages are obtained.
[0047] The method provides better adhesion and anti-tarnish property than Sodium Thiosuphate based silver plating and is less hazardous than Cyanide based silver plating.
[0048] The method is environment friendly and does not have any negative effects on health of the operator working in the industry.
[0049] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.