FIELD OF INVENTION
The present invention relates to co-deposition of copper and zinc from a single bath on steel cord adaptable to reinforcement in rubber tyre.
BACKGROUND OF THE INVENTION
For many years steel tyre cord has been used as a reinforcement material in automotive tyres. Most important for the success of steel cord was the invention of the radial tyre at a time when steel tyre cord showed significant quality advantages in application behavior over other reinforcement materials. Europe was the birth place of steel tyre cord and the first steel tyre cord quantities were produced there followed by Japan and later by the United States. Today China has the biggest growth in steel tyre cord manufacturing capacities followed by Eastern Europe and Brazil.

The yearly consumption figures of steel tyre cord since 1970 has been shown in Figure 1.
The pioneer development work in the application of steel tyre cord as tyre reinforcement material was done by the French tyre producer Michelin, who found out very early the advantages of steel cord in tyres with a thin brass layer as the qualified coating material.
The brass layer has an excellent metallic bond with the steel in the wire surface by the solid solubility of copper and zinc atoms in Iron and reverse. On the other hand the chemical bond between the brass layer and the rubber of the tyre shows superior qualities in the adhesion behavior. In addition the very ductile brass layer shows excellent lubrication qualities in the wet drawing process which makes this process step possible and efficient.
The brass plating technology plays a key role in the steel tyre cord manufacturing process and has a dominant influence both on the quality performance of the final product and on the manufacturing costs of steel tyre cord.
The sequential brass plating system with the deposit of a copper layer in the first step followed by the deposit of a zinc layer in a second step represents the frequently applied multi wire process.

The two layers of copper and zinc will be transformed into homogenous brass in a separate diffusion annealing process.
The process map for the existing conventional technology for the plating line has been shown in Figure 2.
Salient Features of Brass Plating Line
A. The investment for brass plating = 25% of total investment for producing
tyre cord
B. Impact of brass plating line on the production and quality = 50%
C. The importance of the plating line equals with the quality of raw material or
even higher
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose co-deposition of copper and zinc from a single bath on steel cord adaptable to reinforcement in rubber tyre which eliminates the disadvantages of prior art. Another object of the present invention is to propose co-deposition of copper and zinc from a single bath on steel cord adaptable to reinforcement in rubber tyre which saves production time.

A further object of the present invention is to propose co-deposition of copper and zinc from a single bath on steel cord adaptable to reinforcement in rubber tyre which lasts long life of steel cord.
A still further object of the present invention is to propose co-deposition of copper and zinc from a single bath on steel cord adaptable to reinforcement in rubber tyre which is eco-friendly.
SUMMARY OF THE INVENTION
In present innovation brass plating of tyre cord from a single bath has been envisaged. The process would use single plating bath and same power supply for the co-deposition of Cu and Zn. This can be achieved by use of complexing agents to bring deposition potential of Cu and Zn closer. The plating line operated at current densities of 5-10 Amp/cm2 with cyanide complexing agents could achieve this.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1- shows a statistical data for worldwide steel cord consumption. Fig.2- shows a process chart for brass plating line in prior art.

Fig.3- shows a polarization plot showing limitations of the conventional process for co-deposition of Cu and Zn from a single plating both.
Fig.4- shows a polarization plot showing co-deposition of Cu and Zn from a single bath by use of complexing agent.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The complex bath comprising a mixture of:
(1) Copper cyanide at 50-75 gm/litre;
(2) Sodium cyanide at 90-130 gm/litre;
(3) Zinc cyanide at 15-30 gm/litre;
(4) Sodium hydroxide at 40-50 gm/litre;
are taken in a large metallic container which is used as anode. The steel cords are immersed in the bath and used as cathode. The container is heated from 50-75°C by means of an electrical auto controlling heating means. Now the plating of brass starts by applying a current density 5-10 Amp/cm2 in the system (fig 4). Within 2-3 min the metallic deposition of 1 micro meter thick layer takes place. Taking out brass coated steel cord from the bath and washed with water.

WE CLAIM
1. Co-deposition of copper and zinc from a single bath on steel cord comprising:
- a large metallic container which contains a complex bath ;
- the complex bath comprises a mixture of

(1) Copper cyanide at 50-75 gm/litre
(2) Sodium cyanide at 90-130 gm/litre
(3) Zinc cyanide at 15-30 gm/litre
(4) Sodium hydroxide at 40-50 gm/litre

- the complex bath is heated to 50-75°C by means of an electrical auto controlling heating means;
- the large container acts as anode and immersed steel cord in bath is used as cathode;
- applying a current density 5-10 Amp/cm2 for 2-3 minutes;
- deposition of Cu and Zn simultaneously take place up to a thickness of 1 micrometer during this period
Characterised in that the said current density in a single bath containing a cyanide complexing agent capable of plating Cu and Zn simultaneously on steel cord from the heated bath.

2. The co-deposition of copper and zinc from a single bath on steel cord, wherein Cu:Zn ratio exists 50:50 to 80:20 by varying current density and time.
3. The co-deposition of copper and zinc from a single bath on steel cord as substantially described and illustrated here in along with accompanying drawing.

In present innovation brass plating of tyre cord from a single bath has been envisaged. The process would use single plating bath and same power supply for the co-deposition of Cu and Zn. This can be achieved by use of complexing agents to bring deposition potential of Cu and Zn closer. The plating line operated at current densities of 5-10 Amp/cm2 with cyanide complexing agents could achieve this.