SUPER BRIGHT NICKEL BRIGHTNER - 607/633

BETTER PERFORMANCE BRIGHT NICKEL PROCESS

"Super  bright  nickel process" is a better  performance  process developed to produce superior levelled, ductile, brilliant deposits of  mirror  finish  with uniform brightness  at  medium  and  low current  density  area,  acceptable coverage  and  better  chrome receptivity.

The  process  employs  two addition agents  namely  super  bright nickel brightner 607/633 and additive 602/622. Both the  addition agents are required for initial bath make up and for replenishing primary and secondary brightner components during working of  the bath  solution.  The process gives excellent performance  over  a wide range of operating bath concentration, temperature,  current densities etc. And can be used for either rack or barrel  plating application with air or mechanical agitations.

The  process is used for decorative plating either for  a  single layer  bright nickel or as the top layer over  semibright  nickel for  improved corrosion resistance. This process can be  used  on different  base metals such as m.s, copper,  electroless  nickel, semibright  nickel and on brass, zinc and zinc alloys  components with a previous copper plating from a cyanide based process while on  aluminum  and  aluminum alloys  after  suitable  pretreatment followed by zincating and cyanide copper plating.

Salient features : 

1)   faster rate of brightening provides desired finish with less thickness of the deposits. 

2)   produces  extremely goods levelling  resulting  in  shorter plating time and fewer polishing operations. 

3)   consist  of wide bath chemistry range helps in  easy  plant control, replenishment and does not require
      frequent  batch treatment.

4)   excellent low current density brightness and coverage.  

5)   excellent deposit ductility and chrome receptivity.  

6)   good tolerance to metallic impurities.  

7)   highly  stable brightner and additive system  and  in  some applications super brightner-607/633 alone can
      be employed.  

Bath Make-up :                                                             Rang           Optimum

Super bright nickel salt 601/631  gm/lit                         200-400            325                   

Super bright nickel additive 602/622 ml/lit   (vat)             6.0-10.0            8.0

                                                              (barrel)         4.0- 8.0             6.0

Super bright nickel brightner 607/633 ml/lit (vat)             0.4- 0.8             0.6

                                                              (barrel)         0.2- 0.6             0.4  

Working conditions :                Rang           Optimum

Density *Be                        16 - 26           22

Temperature *C                   40 - 60           50  

Ph(electrometric) (vat)          4.4 - 5.2         4.8  

                      (barrel)          4.0 - 4.8         4.4  

Cathode current density                      

               (vat)amp/sq.dm     2.0 - 8.0         4.0  

           (barrel)amp/sq.dm     0.5 - 2.0         1.0  

Anode current density

              (vat)amp/sq.dm      1.0 - 4.0         2.0  

          (barrel)amp/sq.dm      0.5 - 2.0         1.0  

                     voltage(vat)      4.0 -12.0          5.5  

                           (barrel)     8.0 -16.0         12.0  

                        Agitation   cathode rod/low   Air  

                                          pressure air  

Filtration                            continuous      continuous     

Rate of deposition at
3 amp/sq.dm.per minute      0.50 micron       0.58 micron  

Bath maintenance :  

Nickel metal              gm/litre          43- 70         61.0

Nickel sulphate          gm/litre        170-270       230.0

Nickel chloride           gm/litre          32- 55          48.0

Boric acid                  gm/litre          30- 50          45.0

Consumption :     High Levelling     Medium      Higher
                           Low Thickness  Thickness   Thickness
                
                             less than 10     2-15           More than
                              microns         microns      20 microns    

Super Bright Nickel 
Brightner 607/633    250     255    175   150      125       115 ml/1000 amp-hr.

Additive 602/622      250     200    175   125      125         80 ml/1000 amp-hr.

Leveller 544/644-        75                75                            50  ml/1000 amp-hr


Bath Solution Preparation : 

The recommended solution reparation procedure is give as under :

1) Leach a new rubber lined thank and filter unit with 50 ml/lit of sulphuric acid and 1.0 ml/lit of antipit 594.
    Agitate the solution for few hours and the acid solution is allowed  to stand over night. Afterwards the
    cleaning should  be  done with fresh water containing 2ml/lit of antipit-594 followed by thorough cleaning with
    water.

2) Fill  the  cleaned  and rinsed  plating  tank  about  three quarters full of softened or demineralised water. Heat
    to  a    temperature of 55*-60*c.   

3) Add  the requisite quantity of bright  nickel  salt-601/631, stir vigorous until completely dissolved. 

4) Dilute the solution to the working level and add  sufficient nickel carbonate slurry and stir the solution
    vigorously  to rise  the ph value to 5.2-5.5 add 1.0 ml/lit of 100  volumes   (30%) hydrogen peroxide (lr.grade).
    Stir vigorously at  55*-     65*c for two hours.

5) Add 2 gm/litre of nicko purifier c-536 and 2gm/litre of nicko purifier 534, air agitate the solution for 2 hours. 

6) Allow the solution to  stand overnight to enable the  carbon and other residues to settle.

7) Filter  the  solution  through filter pump  in  to  a  clean container, taking care not to disturb the layer of
    sludge at  the bottom of the tank. Take out the bottom portion into  a   narrow container, allow it to stand for
    few hours and filter.

8) Bring back clear filtrate into thoroughly cleaned and rinsed   plating  tank. Adjust the ph to 4.5 using  dilute 
    sulphuric     acid(20%)

9) If necessary  electrolyze  the bath  solution  at  0.2-0.5   amp/dm.sq.  Using corrugated scrap dummy ms 
   cathodes,  with  air agitation at 50-55*c temperature and keeping  filtration  continuously for 8-12 hours or until
   recesses in  corrugated cathodes are light in colour.  

10)  add  required quantities of brightner 607/633  and  additive 602/622. Now the bath solution is ready for use.

Equipment :

Plating tank :

The  plating  tank  should be of mild steel  and  lined  with  anapproved grade of  semi hard or hard rubber. The quality  of  the rubber  is  very  important  for good  performance  of  the  bath solution.  To  save  heating  cost in  large  operations,  it  is advisable to provide thermal lagging from outside.  

Heating :  

The   plating   tank   should  be  equipped   with   a   suitable thermostatically controlled heating device to heat the  solution. Silica cased electric immersion heaters with suitable  protective cages  or  titanium  cased electric heaters  can  be  used  where electrical  heating  are  provided  in  small  or  medium   scale operation.  While  titanium heating coil is used where  steam  or thermic fluid is used for large scale operation.

Filter unit : 

Continuous  filtration  during  operation  is  recommended.   The capacity of the filter unit should be such that it should  filter the solution at least double the volume of the tank per hour. All the  inside parts of the filter unit should be made up of  either approved hard rubber plastic or chemical resistant type aisi  316 stainless steel. 

Agitation :  

Low pressure, oil free air equipment is recommended for agitation of the bath solution. The air agitation coil should be made up of either pvc, ebonite or polypropylene. Compressed air coming  from a conventional air compressor should be used.  

Role of bath constituents : 

Nickel sulphate :  

This  is the main source of nickel ions and the concentration  of these  largely  determine  the limiting current  density.  A  low concentration will reduce cathode efficiency, rate of deposit and will increase the plating time to deposit the desired  thickness. While  a high concentration allows the bath to operate at  higher current densities.  

Nickel chloride :

Nickel  chloride  is  essential in a nickel bath  to  enable  the anodes to dissolve correctly without polarisation and to  improve the   electrical   conductivity   of   the   solution.   Chloride concentration  higher than 70 gm/lit should be avoided  since  it will  adversely affect the ductility of the deposit and is  never recommended while low concentration causes anode polarisation and increases brightner consumption resulting in cloudy deposits.

Boric acid : 

Boric acid is highly important constituent in nickel bath,  hence its concentration should be checked once a week and maintained to 45  gm/lit.  It acts as a buffer to maintain the ph of  the  bath solution  within  a  certain  range,  helps  to  provide  deposit ductility, adhesion and brightness, prevents high current burning and pitting and maintains proper cathode efficiency. It minimizes an  increase in ph in the areas closer to the cathode  and  hence prevents  the formation of metallic hydroxides from any  metallic impurities, especially iron. 

Otherwise  these  hydroxide  compounds would be  include  in  the deposit,   resulting  in  brittle  and  burnt  deposit.  A   high concentration   of  boric  acid  is  not  harmful  to  the   bath performance  except  that  it can lead to roughnes  if  the  bath temperature  drops  below  42* c. In  case  of  high  boric  acid concentration, the bath solution can be cooled to 32*c & filtered to  remove excess boric acid or otherwise its addition should  be stopped until the concentration drops to the optimum level. 

Super bright nickel additive 602/622 :  

Additive  602/622  is  required  for  initial  make  up  and  for maintaining  the  bath  along with brightner  607/633.  The  main function of 602/622 are to improve the ductility of the  deposit, to act synergistically with brightner 607/633 to maintain maximum brightness  and  levelling,  as  well  as  low  current   density brightness and coverage. If its concentration decreases below the recommended  levels,  it  usually  causes  sluggish  response  to addition  of brightner 607/633 and lead to hazy dull  deposit  in the  high current density area, decreases the  deposit  ductility and  increases  chrome  coverage  problems.  It  is  consumed  by electrolysis  and removed by drag out losses as well as  to  some extent by continuous filtration through a carbon pack and by bach carbon treatment. The overall consumption of the additive 602/622 depends on the bath solution composition, operating  temperature, ph,  purity of the solution, degree of ductility,  levelling  and brightness required, quality of the base metal and final  surface finish required. 

Super0 Bright Nickel Brightner 607/633.

This  is  the  main  strong brightening  agent  used  along  with additive  602/622  and or with leveller 544/644. It  is  used  to maintain  maximum rate of levelling and brightness to get  mirror finish.  A  low concentration will result in an overall  loss  of brightness,  levelling  and performance. So it  should  be  added regularly  along with other addition agents to obtain  consistent results.

It is mainly consumed by electrosis but minor losses are also due to  drag out and absorption in carbontreatment, anode bags,  tank lining etc.to  maintain  consistent result with  required  concentration  of these  addition  agents, they are added on the basis  of  ampere-hours  passed. The normal consumption rates for 1000 amp/hr.  Are given as under :  

Super Bright Nickel Leveller-544/644. 

This  is  a  specially formulated product to  boost  the  deposit brightness,  reflectivity  and levelling. It is used  along  with additive  602/622  and brightner 607/633. The  rate  of  addition should  be  directed as per the finish required and it is  to  be control with in the range as mentioned in above table. 

Antipit : 594 and 595 :  

These are wetting agents, used in bright nickel bath to lower the surface tension of the bath solution to facilitate elimination of hyrogen  generated  on  the cathode surface and  to  get  rid  of pitting   problems.  These  are  normally  incorporated  in brightner  formulation  and  extra additions  are  not  generally \required. Additions of these are recommended only if the  g is observed.  

Bath solution operation and control :  

Temperature :  

To  produce  best  results, the bright  nickel  baths  should  be operated at 50-55*c. Higher operating temperatures permit  higher current  density  to be used and improve  degree  of  brightness, levelling  and ductility. If the bath solution is contained  with metallic impurities more than the optimum level, it is  advisable to  work at lower operating temperature temporarily before  batch treatment. Lower the operating temperature, lower will be current density,  rate of deposition, brightness and  levelling.  Finally this leads to higher plating time to get required finish. 

Ph : 

The bright nickel process is operated at a wide ph range of  4.4-5.2  it  is  recommended that ph of the  solution  be  maintained within the specified range. Higher levelling, brightness, clarity etc.  With  less ductility of the deposits are obtained,  if  the bath is operated at the higher end of the range i.e. 4.8-5.2,  ph higher  than 5.2 decreases the ductility of deposits  and  causes high current burning and roughness due to encroaching of iron and aluminum  hydroxides in the deposit. It also affects  the  chrome receptivity. Lower ph values less than 4.2 can cause overall dull deposit,   the   high  current  burning,   pitting   and   higher consumptions  of  the  brightner and  additive  to  maintain  the acceptable  finish. In normal working the bathe ph value  of  the solution  tends  to  rise. The ph value  should  be  checked  and adjusted  at least twice in each working shift by  adding  dilute sulphuric  acid(20%  by volume) of good quality. In case  of  low anode  area  and clogging of the anode bags due  to  excess  iron contamination,  the rate of ph shifting to higher values  becomes faster.  This leads to higher amount of the acid  requirement  to maintain the bath in the proper range.  

Current Density :    

The  total  current  to the plating tank  divided  by  the  total cathode  area and anode area are called cathode  current  density and  anode  current  density  respectively.  The  process  allows plating  over  a  wide operating current  density  range  without burning, but an average cathode current density of 4.0 amp/sq.dm. And  anode  current density of 2.5 amp/sq.dm  would  be  normally used.  Very low anode current density is not  detrimental  except that the nickel metal content can rise during production. In case of  very low anode area. Anode current density will be very  high and  can cause anode polarization. Severe anode polarization  may generate  chlorine gas at the anode this will drastically  effect the consumption of brightner and additive.  

Sources of contamination and purification :  

Source of metallic contamination in nickel bath are nickel  salt, sulphate,  chloride,  make  up  water,  dripping  from   busbars, dissolution  of  metal from tubular articles during  plating  and from  articles dropped in to tank, accidental addition  of  wrong salts,  drag  in  from strike solution or  pickles  and  improper anodes.  During  plating  organic  impurities  enter  in  to  the solution  via  drag  in or per-treatment  solutions  and  electro decomposition of addition agents due to anode polarization. These can be removed by oxidation carbon treatments.

Inorganic  metallic impurities like zinc, copper and lead can  be effectively removed at low ph of 3.5 with high air agitation  and high temperature by electrolytic dummy treatment using corrugated ms  dummy cathodes at a low current density of 0.2-0.4  amp/sq.dm  chromium contamination of hexavalent chrome can be eliminated  by adding  the  calculated  quantity of lead  carbonate  or  ferrous sulphate so that lead chromate or chromium sulphate  precipitates and is removed by filtration at 5.2 ph. Take care to avoid excess addition  as  otherwise it will lead to dark  deposition  in  low current  density  area. Iron can be removed by  oxidation  carbon treatment as described in removal of organic impurities.

Organic contamination is generally removed by carbon  absorption. When  the contamination is not severe, the bath solution  can  be continuously  filtered  through a small amount of  mahavir  nicko purifier c 536 and purifier 534 packed with in the filter. If the contamination is severe, frequent and larger purifier packs  will be  necessary,  when  high ph oxidation  treatment  is  the  only alternate   to   remove   organic   impurities   from   seriously contaminated  bath solution, it is to be carried out as  follows. Heat  the solution to 60*c.remove anode baskets and clean  anode-bags.  Raise  the ph value to 5.2-5.5 using nickel  carbonate  or caustic  soda.  Add  0.8-1.2 ml/lit  of  hydrozen  peroxide  (100 volume,30  % ) or 0.5-1.0 gm/litre each of nicko purifier  c  536 and  nicko purifier 536. Air agitaion vigorously for at  least  2 hours.  Allow the solution to stand overnight  without  stirring. Filter  the  clear  solution from top in  to  the  clean  plastic containers without disturbing the layer of carbon sludge  settled at  the  bottom  of  the plating  tank.  Remove  the  sludge  and thoroughly clean and rinse the plating tank, anodes, anode  bags, etc. Transfer the solution in to cleaned and rinsed plating tank, put  anodes baskets. Adjust the ph value to 4.5 and  restart  the work.

Note :

Our  recommendation are made in good faith and the based  on  our skill  and  experience however, since the conditions  of  use  of these  products are beyond our control this information is  given on  the express condition and agreement that "  mahavir  chemical industries "  will not be liable to any person by reason there of nothing  here in shall deemed to be a recommendation to  use  any products in violation of any existing patent rights.