SILVER PLATING

Silver is a precious metal . Requirement of  Silver plating  come maximum from electronics industry and jewellary  industry . In electronic industry silver plating is more prefereble because silver has highest electrical conductivity compared to all other metals. Silver have excellent solderability.

Silver plating have three types of finish in the terms of appearance :

 1. Matt  
 2. Semi bright and
 3. Bright.

For electronic Industry matt and semi bright finish is more suitable because bright finish conductivity can be reduce due to organic brighteners in the plating bath.

For Jewellary  industry silver plating is decorative purpose so they need mirror type bright finish.

At Present, Maximum silver plating done by cyanide base process. Slowly Non- cyanide silver plating introducing in the market by some manufacturers like epi .

Silver plating process :

1.  Pretreatment  process ( Depend on base metal like copper, aluminium, brass etc)

2. Undercoat coating ( optional)

3. Silver strike

4. Silver plating

5. Anti Tarnish coating

Quality Control :

1. Physical appearance Inspection
2. Adhesion Test by Adhesive tape
3. Thickness test by thickness tester
4. Anti Tarnish Test

SILVER  ANTI TARNISH  TEST  PROCEDURE :

Take 1 ml of 20- 24 % by weight ammonium or potassium sulphide, mix the 1 ml ammonium sulphide solution In 1 litre D M water.

Take  the 1 drops  solution from above 1 litre solutionand drop on the silver plated component, upto 5 min surface should not be change to brown or black. 

CONDUCTIVITY OF VARIOUS METALS 

Material	RESISTIVITY OHM PER METRE at 20 °C	CONDUCTIVITY SIEMENS PER METRE at 20 °C
Silver	1.59×10−8	6.30×107
Copper	1.68×10−8	5.96×107
Annealed copper	1.72×10−8	5.80×107
Gold	2.44×10−8	4.10×107
Aluminium	2.82×10−8	3.5×107
Tungsten	5.60×10−8	1.79×107
Zinc	5.90×10−8	1.69×107
Nickel	6.99×10−8	1.43×107
Lithium	9.28×10−8	1.08×107
Iron	1.0×10−7	1.00×107
Platinum	1.06×10−7	9.43×106
Tin	1.09×10−7	9.17×106
Carbon steel (1010)	1.43×10−7	6.99×106
Lead	2.2×10−7	4.55×106
Titanium	4.20×10−7	2.38×106
Stainless steel	6.9×10−7	1.45×106
Mercury	9.8×10−7	1.02×106

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A  LAYMAN  CAN BECOME EXPERT

Internet is a boon to enhance the  knowledge in today’s world if you use smartly Internet is now move beyond the email service . Earlier people use internet maximum for sending the  e-mails , even today also some people use internet for only e-mail purpose only . e-mail service is more popular because of necessity . e –mail is need of today. Earlier people send letters in hard copy but today same letter move in soft copy through e mail . Beyond the e mail people now use internet for maximum information purpose . All this happen because of search engine like google. If want to search anything and log in to google you can get all information . Some people use this technology for entertainment purpose , some people use for information purpose , some people to enhance their knowledge . I am also belong to later  category . I learnt a lot of things from internet through google .

I know one of known person who  is uneducated  and drive auto for his livelihood . He is uneducated but not a fool . He was having a strong determination to come up in the life . He started a plating plant . During doing the plating of various component . He want to know about the manufacturing process of component but his customers never tell anything about that component . He asked to many people but he not got the required information then someone suggest him to seach on google .

He start using the google for searching the information . Initially he faced a lot of problem to operate the computer because he was a just layman for the computer but slowly  he transforms  himself from a layman to expert in his field by using internet  through  youtube . He used the this technology for informative purpose . He treat the computer as a class and google , youtube , yahoo etc as a teacher and contents of them as a book to learn  his subject . Today he is having two small manufacturing unit . Here I don’t want to say that because of internet he come up in the life . There was various factors but internet help him lot to enhance his knowledge . Like him may be so many people will be  in this world who got the information from google and youtube which they can’t get so fast from other source . They can only explain properly the benefit of internet , who got it from this. 

QUALITY  CONTROL

 Electroplating is the science but  chemistry of QUALITY CONTROL is math where required proper calculation & planing .  The most job platers looking at the end of day  more production and less rejection  as well as to meet the customers requirement in terms of quality , delivery .  We can't acheive this to by this telling to people like operator, supervisor, manager etc , or by a casual approach .  To acheive this need proper planning with a new systematic approach .

Before doing the process properly understand the customer requirement & Specification and then plan for process .

Bath maintenance : 

Always maintain the bath constituents in the recommended  limit range by doing regular bath analysis in the lab . Change the water rinse bath at frequent interval . Filter or Decant  the bath to keep the bath solution clear as much possible to minimise the contaiminations .

Process parameters control :

Maintain the process parameters like temperature , current , process time ,ph, proper water rinse etc  as per control plan and record them .

Inspection

Inspection coming in the two stage. First, Inspection of parts before processing like dents,damages etc and second after finishing the process like thickness,adhesion,brightness,roughness,salt spray test etc  .

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   AUTOMATIC PLATING PLANT                            

MANUAL PLATING PLANT

AUTOMATIC PLATING PLANT

At present  maximum plants are running manuals. Reason may be various  but now time has come for bulk job platers to switch from manual plant to automatic plant. In manual plating process operators carrying the each jigs from one tank to next tank for next process but in the fully automatic plating plant components will carrying commonly in racks ( with many  jigs ) by mechanically  through a number of treatment cycle tanks , which is controlled by PLC operated  transports wagons .

The advantages of Automatic plants are direct savings in  labour  cost, consistency in quality, Better  control of process application, production, Improved solution maintenance , quality and specifications , Lower floor space, Better control of drag out, Lesser danger of solution contamination, Efficient fume extraction and ventilation, High quality ETP process. Improved working environment , less rejection .

NEW PLANT      :          ZINC PLATING                               

Many people ask that I want to start a zinc plating plant but they don’t anything about zinc plating except that they having the orders. Doing zinc plating is not a tough job if you do in a systematic way . Here also I just want to share the same information that what a person need if he want to start a new zinc plating process .

EQUIPMENTS  :

1.       Rectifier   500 AMPS and  15 volt  : To supply the current for plating

2.       PP Tanks  for Pickling,degreasing, plating ,passivation ,water rinse etc. Tank sizes can vary    depends on parts, which you are expecting .

3.       Filter machine : To filter the bath

4.       Oven : To dry the plated component

5.       Thickness tester :  To check the coating thickness

6.       Others  accessories like heaters,timers,lab, chemicals, anodes etc.

7.       Fume Exhaust systems, ETP Requirement as per Local PCB Board .

LEGAL  REQUIREMENTS  :

1.       Registration to  Govt  sales department .

2.       Local Pollution control board consent.

OTHERS  REQUIREMENTS  :

1.       Place :   Minimum 1200 square feet for a small plant .

2.       Qualified Experience Operators.

3.       Chemist .

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 NEUTRAL  SALT SPRAY TEST                                                    

When we do plating to our customers , they ask a specific hours to pass the salt spray test .Salt Spray Test  is a standardized test method used to check  corrosion resistance of plated components.We should do the plating such a way that component should the pass the particular hours in salt spray test . Salt spray test is an accelerated corrosion test that produces a corrosive attack to the coated samples in order to predict its suitability in use as a protective finish. The appearance of corrosion products  is evaluated after a period of time. Test duration depends on the corrosion resistance of the coating; the more corrosion resistant the coating is, the longer the period in testing without showing signs of corrosion.

 Salt spray test is done by as per ASTM ( American Society for Testing of Materials) 117  standards.  These standard describe the necessary information to carry out this test , like apparatus, procedure and  testing parameters such as temperature, air pressure of the sprayed solution, preparation of the spraying solution, concentration, pH, etc. This standard is just a reference standard . However, these testing standards neither provide information of testing periods for the coatings to be evaluated, nor the appearance of corrosion products in form of salts. Requirements shall be agreed between  customers and manufacturers.

Salt spray test done for two things, first we do for WHITE RUST and second do for RED RUST .

COST SAVING PROCESS

 LOW TEMPERATURE ALKALINE IMMERSION DEGREASING 

 To clean the oil grease etc from steel component , there are so many process  available for us, which depends on oil layer ,application, finish requirement , suitability etc but  at present most popular  process is alkaline immersion degreasing  hot process, which require the bath temperature between 50 to 90 degree centigrade .

To do the degreasing at the high temperature  we face some problem like :

1.   During starting the process at morning time  we not able to get the high temperature of bath UNLESS we have to on the heater with cut off system before of that day to achieve the bath temperature of degreasing bath.

2.   IF we on the heater too much before the working time to get the specified temperature THEN we are allowing the degreasing bath to consume more power .

3.   Running the degreasing bath at high temperature also bath will consume more power .

4.   IF by chance we not able to provide the specified temperature due to power cut or any other reason then component will not clean proper .

   To overcome the above problem many degreasing chemicals manufactures developed the low temperature alkaline immersion degreasing salt with better surfactant , which will be clean the oil, grease etc from your steel component at low temperature ( 25 to 50 degree centigrade) . By adopting this low temperature alkaline immersion degreasing process we can avoid the tension of maintaining the high temperature of degreasing bath and power bill also will reduce .

"SAVING THE MONEY IS EARNING THE MONEY "

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 Electroless nickel                                   

What is the electroless nickel :

Electroless nickel means in general terms nickel plating without current , but in chemical terms electroless nickel plating is an auto-catalytic reaction used to deposit a coating of nickel on a substrate. Electroless nickel plating requires no anodes, power supply or electrical connection of any kind. The process simply  mixing  some solutions, heating them to just off the boil, and then immersing the part to be plated. An auto catalytic electrochemical reaction takes place and the nickel is evenly deposited all over the part being plated. The thickness of the plate will depend on the duration of immersion. To stop the reaction, remove the part from the solution. 

 In Nickel  electroplating, it is  necessary to pass an electric current through the solution to form a only nickel  deposit and in electroless nickel deposit , deposit of coating will be phosphorous along with nickel .

Normally we do nickel  electroplating for decorative purpose but electroless nickel coating applied maximum for engineering and functional purpose like hardness , wear properties , corrosion resistance , lubricity, less porosity ,high temperature resistance  (upto 1200 degree centigrade) etc.

The demands of Electroless nickel coating come from oil and gas, printing, aerospace, electronics, medical and surgical parts, chemical processing , automotive industry etc .

Why we do electroless nickel:

Electroless nickel is costly compare to nickel electroplating but some people ask for electroless nickel coating instead of cheaply available nickel electroplating and they are ready to pay for that, why ?

ADVANTAGES :

1.       When we do Electroless nickel plating we get overall uniform thickness on the whole surface of  parts , here will be not any high or low  current density area  because here we don’t pass the current . which we can’t achieve in nickel electroplating .  

2.       In electroless nickel coating we can get the hardness of component upto 800 VHN .

3.       Can deposit the high thickness.

4.       Electroless nickel suitable for brazing and melting

Types of electroless nickel Process :

1.        Low  phosphorous process

2.        Medium  phosphorous  process

3.       High  phosphorous process

Electroless nickel process  is an auto – catalytic reaction at a particular temperature, Ph, Loading area and balanced chemicals . For a proper electroless nickel bath required following chemicals :

1.        Source of nickel ions

2.        Reducing agent

3.        Complexers,

4.        Neutralizers/buffers

5.        Stabilizers and  

6.        Brighteners.

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