Metal finishing Q&As since 1989

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Electrically Conductive Anti-tarnishing Lacquer for Brass Terminals

2000

Q. Dear Sir , We are on the lookout for suppliers of Electrically conductive Anti-tarnish lacquer for coating on Brass terminals.

We are a leading manufacturer of Wiring Harnesses in India . The Wiring Harness is a bundle of Automotive wires , the ends of which carry often brass / copper terminals ñ either as a free end or inserted into a plastic connector ( with mating terminals inside ) . The terminals in most cases are plated with Tin or Nickel .

Our Main Problems are as below:

1. Corrosion of Tin Plated Brass Terminals ( Cu ~ .3 to .5 microns + Tin 1- 2 Microns )
2. Corrosion of Nickel plated Copper Battery Terminals ( 10 ± 2 Microns )
3. Tarnishing / Blackening of unplated Brass Terminals .

I. We have four types of sources for the terminals :

1. Imported ready to use terminals
2. Terminals manufactured using imported Brass strips .
3. Terminals manufactured using indigenous Brass strips ( ETP quality 70:30 or 67:33
   generally with grades varying from quarter hard to full hard ).
   The terminals are either chain type ( i.e. continuous reels ) or separate .
4. Battery Terminals ( separate pieces ) using indigeneous ETP grade copper .

II . Manufacturing Process of Brass Terminals

1. The Brass strips received in bright condition are processed in the stamping line to form chain terminals. During the stamping process,the strips are sprayed with an Anti-rust Castrol Brand oil.The chain terminals are then inspected & wound on a reel . The terminals are often plated with Tin as slated above . The overall plating thickness is in the range of 1 ñ 2 microns.
2. The Tin Plating Process at Vendorís Premises :

a) Pickling , cold water rinsing , Cu plating , Cold water rinsing , Tin Plating stage 1, Cold water rinsing , Tin Plating stage 2 , cold water rinsing , air drying , winding into reels .

III. Manufacturing Process of Copper Battery Terminals

1. The Copper strips received in bright condition are processed in a press line , to form individual terminals. The terminals are then inspected & sent for Nickel plating ( 10 ± 2 Microns ).
2. Rack Type Nickel Plating at Vendorís premises is as below : a) Bulk dipping process - in Kerosone oil , cleaning with saw dust , HCl washing , cold water rinsing , cathodic cleaning , cold water rinsing ( twice ) , b) Loading in jigs & dipping ñ in H2SO4 washing , Cold water rinsing ( 2 times ) , Nickel Plating , cold water rinsing ( 4 times ) , centrifugal drying , packing .

IV. Problems with Brass Terminals Unplated

(1) Terminals getting tarnished , in as short a period of 1-3 months from the date of manufacture .The problem becomes acute in the rainy & winter seasons. The Brass strips are received from vendors ( Indian Smelting Co. ñ Mumbai ) with the supplier recommended life of about 3 months only ( for brightness ) . Even some of the imported strips have the same problem .

V. Problems with Tin Plated Brass Terminals

1. Low life of 16 hrs in Salt Spray test , against specified 50 Hrs. Minimum .
2. Blackening of Terminals within 1 to 3 months .

VI. Problems with Tin Plated Brass Terminals

1. Non-uniform plating thickness ranging from 7 to 20 microns against 10±2 microns .
2. Peeling off

VII. Customer Complaints due to above

The Customers want the terminalsñ(either unplated brass or Tin Plated brass , or Nickel plated Copper ) to appear bright irrespective of environmental conditions , till the Wiring Harness gets used up in the vehicle & the vehicle gets despatched . A Wiring Harness that gets manufactured ( 1 to 2 weeks from strip stage for the terminals ), may lie with our customersñfor 4 to 8 weeksñ(waiting to be assembled in the vehicle) .

VIII . Our Other Findings & Observations

1. The imported ( Japanese ) unplated brass terminals have a life of 2 to 3 years without tarnishing .
2. (Our R & D have conducted electrical tests on such tarnished terminals & Tin Plated Brass Terminals (using indigeneous brass strips) and have not found any significant difference in electrical conductivity & as such there is functional problem .

Of late customer complaints have become chronic & we are really unable to lick the problem effectively . Efforts are on trying out Electroless Nickel plating of Nickel Plated Copper Battery Terminals . The results are good , but cost wise very high .

We also understand that some electrically conductive lacquers are available ( with negligible deposits ) , which when coated , prevents or delays tarnishing of unplated brass terminals, without affecting the electrical conductivity of the terminals . But we are unable to locate the source for the same .We seek your assistance in locating a few suppliers of such lacquers . Hope you will be able to help us out .

With Regards, R.Vishwanathan

Rajagopalan Vishwanathan
- Noida -.India

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Q. Sir,

Am also looking for a low cost solution in the area of CLEANING machined copper conductor surface area; that will improve the shelf life of the same.

Kindly advise

Thanks & Regards

CHIKKU BABU
- Ernakulam, Kerala, India
August 21, 2009

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Q. Is there any chemical or any method to retain the electrical conductivity of copper yet prevents its tarnish??? If so, can you post its name? (or the method of doing?)

Arun Banik
- Kolkata, India
April 26, 2012

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Q. Will this treatment work for silver plated busbars also?

Nitin Jhaveri
- Vadodara, GujRat, India
August 27, 2017

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Q. Dear Sir,

Anti Tarnishing of Brass and Copper Terminals and lugs. Please give your valuable information of process to prevent Electrical connecters of Brass and copper from oxidation and thereby turning blackish.

Waiting eagerly for your valuable reply.

Sandeep Modi
Quality search - Mumbai INDIA
September 16, 2017