TROUBLE SHOOTING

  TYPICAL DATA FOR CYANIDE COPPER PLATING BATHS
 
Components of the bath Strike bath Rochelle salt bath High speed bath
 CuCN    gm/lit 22 25 60
  NaCN     gm/lit 35 35 -
  Or KCN   gm/lit - - 95
 KoH   gm/lit - - 42
 Na2CO3  gm/lit 15 30 -
Rochelle Salt gm/lit - 45 optional
         
Operational data
Cathode.C.D.A/dm2 1-2 2.0-4.0 3.0-10.0
Anode.C.D.MaxA/dm2 1.0 3.0 5.0
Anode to Cathode   ratio 2:1 2:1 2:1
Anodes El copper EI copper EI copper
Temperature 0c 45-55 45-65 55-65
Agitation Cathode movement Cathode movement Cathode Movement
Filtration Preferred Preferred Continuous Recommended
Uses Strike or thin deposits
Less than 2.5 microns
Strike or thin deposits
Less than 12 microns
Bright or heavy deposit
Less that 60 microns

 

 

 

 
TROUBLESHOOTING GUIDE-CYNANDIDE COPPER SOLUTION.
 

NATURE OF DEFECT

POSSIBLE CAUSE

METHOD OF CORRECTION

POOR ADHESION presence of blister, peeling off apparent if the metal is bent, heated or polished

a. High free cyanide content, indicated by the bright crystalline appearance of the anodes.

a) Analyze the free cyanide content and add the required amount of single copper cyanide. Refer to table below.

b. Low free cyanide indicated by anode polarization, Presence of green smile on the anodes with very little gassing of the solution. In extreme cases the solution may turn pale blue in colour. b) Analyze the free cyanide content and add the required amount of high grade sodium or potassium cyanide to make up to desire level

c. Poor pretreatment Presence of oxide or tarnish, grease, on the substrate metal before plating.

c) Check pretreatment cycle and degreasing solution to ensure their efficiency, view surface of the copper solution and swills for sign of oil or grease, which may carried over from

1. C
revice or trapped holes in the articles,

2. Floating oil from alkaline cleaner

3. External source, like over head machinery.


4. Scale or oxide should be removed by picking or acid dipping prior to plating

Rough granular deposit with dullness and brick red in colour

Too high current density resulting in a burnt deposit. In extreme cases the deposit may be black and spongy in texture.

Plate at a lower current density.

Avoid use of too large and anode surface when plating small parts and distribute such article uniformly in the plating vat or hang them where they are not very near to anodes.

Rough deposit with good colour and appearance particularly on shelf arias.

Presence of suspended solids in the plating solution.

Analyze the free cyanide and correct if necessary. If problem persists, allow bath to settle over-night, then filter or decent the clear solution in to a clean storage tank. Clean out the plating tank before returning the clear solution

Turbid solution

a) low free cyanide as evident by the greenish deposit on the anodes

a) Analyze for free cyanide content and correct by adding the required amount of sodium or potassium cyanide. If analytical facilities are not available, add in small doses like 1-3 g/L till good results are achieved

b) Extraneous matter

b) Remove out insoluble matter

Solution colour green or blue

Absence of free cyanide

Add require quantity of sodium or potassium cyanide after chemical analysis or at least 5 g/l, followed by small doses like 1-3 g/l/ till satisfactory results are achieved.

Very dense solution with crystals deposited on anodes and tank walls.

Accumulation of carbonates generated due to continues decomposition of cyanide over along period of use.

If solution quite old, bell out periodically remove any deposits of sodium carbonate crystals which from during cold weather when the vat is not in use. After wards making up the bath level with water and correct the solution composition by addition of required basic chemicals.

Scanty deposit with excessively high gassing at cathode.

Too high free cyanide or to low copper metal in solution.

Analyze the bath for free cyanide content and if single copper cyanide to restore proper contents of copper metal and free cyanide

Anodes bright and crystalline in appearance

Excess of free cyanide

Analyze and correct as above The anodes should be dark brown in colour in normal operation, and should regain their metallic copper appearance when the bath is idle

Polarized anodes-Black deposit on anodes, reduced current efficiency. This not to be confused with the normal brown coloration

Lead contamination resulting from contact of solution with lead or lead alloy parts falling into the tank. The deposit film is probably lead peroxide

Lead contamination resulting from contact of solution with lead or lead alloy parts falling into the tank. The deposit film is probably lead peroxide

0.3-g/l solution of medium sulphide carefully. This will precipitate lead sulphide and must subsequently be removed by fine filtration

Staining of the copper deposit.

Poor basis metal preparation and due to porosity of the basis metal which oozes out of entrapped cyanide plating solution the copper deposit.

This defect is difficult to avoid completely with casting but can be reduced by rinsing the plated articles several times in cold and boiling water alternately, before they are finally dried. Alternatively immerse the articles, after swilling, in a dilute solution of potassium hydrogen tartarate 5 g/l and again swill before dying. Avoid cutting casting skin during polishing operation.

No copper deposit.

a) Incorrect polarity of current

a) Check polarity of current and correct.

b) Contamination of solution with oxidizing agents like chromic acid. b) Rectification of the solution is difficult. Discard the solution for copper recovery, clean out tank and make up new solution.
c) Passive cathode. c) Remove passive surface by polishing, scratch brushing or etching the articles.

d) Evolution of hydrogen instead of copper deposition on cast iron or lead, due to large excess of free cyanide in solution.

d) Analyzing the plating bath and add single copper cyanide.

 
TYPICAL DATA FOR ACID COPPER PLATING BATHS.
 
Components of the bath General purpose High throw High speed bath
  Cu. Sulphate gm/lit 190-250 60-100 180-250
Sulphuric acid gm/lit 30-75 150-225 30-75
Chloride ion PPM 20-80 30-80 Optional
Addition agents recommended recommended recommended
 
Operational data
Cathode C. D. A/dm2 2-4 1.5-5.0 5.0-50
Anode C. D. max.   A/dm2 2-4 1.0-2.5 2.0-10.0
Anode to cathode area ratio 1:1:5 2:1 1:1.5
Anodes Phosp. Copper Phosp. copper OHFC copper
Temperature 0c 18-30 18-32 18-45
Agitation Air / Mechanical Air / Mechanical Vigorous Air & Mechanical
Filtration Continuous Continuous

Continuous recommended

Uses Under coat, ABS,
Jewelry, Utensils
PCB, Cont Strips, Heavy deposits, Graveure, cladding Copper foil

 

 


 
 
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