Fault
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Possible cause
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Diagnostic clue
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Corrective action
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No plating at all
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Open circuit |
If you are using a MultiPlater, an open circuit is indicated by a continuous red light. A conventional power supply will show zero amps. |
Check the workpiece connection, electrode and leads. Make sure the swab is fully wetted with plating solution so that electrical contact is maintained. If you are unsure whether the surface itself is electrically conductive, check it with the Conductivity Tester before continuing. |
| Connections reversed |
The MultiPlater will still show a green light and a conventional power supply will still show amps. |
Correct the polarity. Nickel and stainless steel will usually only need to be reactivated. Brass and copper may be etched and will need to be repolished before replating. |
| Swab not fully wetted with plating solution |
No current flows if the plating solution does not make contact between the electrode and the workpiece. |
Make sure the swab is fully wetted with plating solution. |
| Trying to plate directly onto a PVD coating |
Little or no gold may deposit. In some cases irregular swirling or streaked marks can appear across the surface, rather like skate marks on an ice rink. The swab may also become dark or gold-coloured as tiny particles of the PVD coating detach and collect on it. |
Do not brush plate directly onto the PVD coating. Remove the PVD coating completely, then prepare and plate the underlying surface. |
| Trying to plate directly onto a passive or difficult-to-plate metal or alloy |
Electrical contact is present, but little or no gold plating takes place. |
Use the appropriate preparation process before gold plating. Medical alloys and passive stainless steels may require Gold Strike, aluminium requires Zincate Dip, and titanium requires alumina grit blasting. |
| Platinum coating on the electrode completely worn away |
If you are using a MultiPlater, a continuous red light will show. A conventional power supply will show zero amps even though the electrical connections are sound. |
Replace the worn electrode. |
| Existing clear coat or E-coating on the surface |
A continuous clear insulating coating prevents electrical contact with the underlying metal, so no gold plates. With a MultiPlater, the indicator remains red because no current is flowing. The coating can be difficult to see and the underlying surface may still look metallic. |
Completely remove the clear coat or E-coating to expose the underlying metal, then prepare and activate that metal using the appropriate process before gold plating. |
Plating is slow
|
Gold content of the solution is depleted |
The solution has been used repeatedly and the plating rate has gradually become slower. |
Replace with fresh Gold Brush Plating Solution, or increase the voltage gradually to improve the plating rate. Take care not to burn the deposit (see below). |
| Swab is not fully wetted/saturated with plating solution |
Plating takes place, but more slowly than expected. |
Make sure the swab is fully wetted and saturated with plating solution throughout the plating process. |
| Swab is too small for the area being plated |
The plating is progressing normally and there is good electrical contact, but it is taking a long time to build the required thickness over the whole area. |
Use a larger swab where practical. Consult the Gold Brush Plating Calculator to select the appropriate swab size and calculate the expected plating time for the area and thickness required. |
| Voltage too low |
There is full electrical contact and plating is taking place normally, but the deposition rate is slower than expected. |
Increase the voltage gradually within the recommended operating range. For Gold Brush Plating Solution this is normally 3–5 V. Stop increasing the voltage if the deposit begins to darken or burn. |
| Swab is not being kept in consistent contact with the workpiece |
Plating occurs when the swab is in good contact, but the overall build-up is slower because contact is weak or intermittent during the process. |
Keep the fully wetted swab in consistent contact with the surface while moving it continuously over the area being plated. |
| Solution or workpiece is too cold |
Plating is slower than usual even though the solution, swab and electrical contact are otherwise satisfactory. |
Allow the solution and workpiece to reach the normal operating temperature range of 14–25 °C before plating. |
| The expected plating time is shorter than the process actually requires |
The plating is proceeding normally, but the area is relatively large or a specified thickness is being built and the process simply takes longer than expected. |
Check the expected plating time using the Gold Brush Plating Calculator for the actual surface area, required thickness and swab being used. |
| High resistance in an electrical connection |
Plating is unusually slow despite otherwise normal conditions. A poor or partially oxidised connection may become noticeably warm or hot to the touch. |
Switch off the power and check all electrical connections. Clean or replace any oxidised, loose or damaged contacts before continuing. |
Plating is patchy or uneven
|
Insufficient activation of the surface |
Gold plates readily on some areas but is reluctant to start, or fails to plate, on others. |
Reactivate the surface before plating. Where practical, rub the surface with MPU. Alternatively, use Activator or, for passive stainless steel, Stainless Steel Activator according to the appropriate process instructions. |
| Surface not properly cleaned |
Plating is patchy or refuses to deposit in some areas. Oil, grease or other water-insoluble contamination remaining on the surface interferes with the plating process and is transferred to the swab. |
Improve the cleaning process, introducing a suitable degreasing stage where necessary. The contaminated swab must also be washed thoroughly with concentrated detergent and then rinsed very well with clean water before being used again. |
| Trying to plate directly onto a PVD coating |
Little or no gold may deposit. Irregular swirling or streaked marks may appear across the surface, rather like skate marks on an ice rink. The swab may also become dark or gold-coloured as tiny particles of the PVD coating detach and collect on it. |
Do not brush plate directly onto the PVD coating. Remove the PVD coating completely, then prepare and plate the underlying surface. |
| Residual brighteners or other strongly adherent residues from previous tank plating |
The surface has recently been tank plated, particularly with silver, and the subsequent gold deposits unevenly or refuses to plate properly in some areas. |
Thoroughly remove residual plating additives before gold plating. Where practical, rub the surface with MPU before proceeding. Freshly tank-plated silver can retain strongly adherent sulphide brighteners which can seriously interfere with subsequent plating. Gold should not normally be plated directly onto copper; use a suitable barrier layer first. |
| Swab contaminated from a previous process |
The swab is discoloured, indicating that it has retained foreign material from an earlier process. |
Wash the swab thoroughly with concentrated detergent and rinse very well with clean water. Replace the swab if the contamination cannot be removed. |
| Clear coat or E-coating only partially removed or intermittent |
Gold plates on exposed areas but not where the insulating coating remains, producing sharply defined or irregular patchy plating. |
Completely remove all remaining clear coat or E-coating, then prepare and activate the exposed metal before replating. |
Deposit is dark/brown/burnt
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Voltage too high |
The gold deposit becomes dark, brown or burnt, particularly on corners, points and other high-current areas. |
Reduce the plating voltage until a normal gold deposit is obtained. Keep within the recommended operating range of 3–5 V. |
| Brushing action too slow or incorrect |
Dark or burnt areas develop during plating, particularly in the centre of the circular motion where the swab is moving slowest relative to the workpiece. |
Increase the speed of the brushing action and keep the swab moving continuously in a circular motion over the surface. Do not move the swab backwards and forwards in straight strokes as though gloss-painting a door. Correct swab movement is a brush-plating skill that improves with practice. |
| Iron contamination |
The gold deposit has a grey-brown appearance. A stainless steel electrode is being used instead of a suitable platinum, carbon or copper electrode. |
Stop using the stainless steel electrode and discard the contaminated solution. Replace the electrode with a suitable Platinum Electrode or Short Platinum Electrode. Alternatively, use a Carbon Electrode or Short Carbon Electrode. |
Plating is dull
|
Underlying surface is dull |
The gold deposit is sound and uniform, but has approximately the same surface finish as the surface underneath. Gold Brush Plating Solution will retain the brightness of the underlying surface, but it will not level it. |
Polish the surface to the required finish before gold plating. If it has already been plated, carefully polish the gold using the appropriate grade of MPU and replate if necessary. |
| Brightener depleted with age |
The solution still plates gold at a normal rate, but the deposit is noticeably less bright than when the solution was fresh. |
Replace with fresh Gold Brush Plating Solution. |
| pH too high |
The solution still plates gold, but the deposit has become dull. Gold Brush Plating Solution has a bright-plating pH range of 3.8–5.4. Contamination with Cleaner, or another higher-pH solution, can raise the pH above this range. |
Do not attempt to chemically adjust the plating solution. If the gold deposit is sound, the dullness can often be polished out using MPU Coarse, MPU or MPU Fine as appropriate. Alternatively, strip and replate using fresh solution, or discard the contaminated solution. |
| Iron contamination |
The gold deposit has a grey-brown appearance. A stainless steel electrode is being used instead of a suitable platinum, carbon or copper electrode. |
Stop using the stainless steel electrode and discard the contaminated solution. Replace the electrode with a suitable Platinum Electrode or Short Platinum Electrode. Alternatively, use a Carbon Electrode or Short Carbon Electrode. |
Plating is peeling or rubbing off
|
Existing plating or coating is poorly adhered |
The gold peels or rubs off together with the plating or coating underneath it. There may already be signs of blistering, flaking or delamination before gold plating. |
Remove all loose or poorly adhered plating back to a sound surface before replating. A new gold layer cannot improve the adhesion of an unstable coating underneath it. |
| Plating directly onto a difficult-to-plate surface or coating |
Gold may initially appear to plate, but adhesion is poor and the deposit subsequently rubs off or peels. This can occur on passive metals and particularly on PVD-coated surfaces. |
Identify the underlying surface or coating and use the appropriate preparation process before gold plating. PVD coatings should normally be completely removed before plating the underlying surface. |
| Surface not properly activated, or allowed to dry after activation |
Gold plates but adhesion is poor and the deposit may peel or rub off. This is particularly important with plateable stainless steels and nickel if the surface is allowed to dry after activation. |
Reactivate the surface immediately before gold plating. After activation, rinse as required but do not allow the work to dry before plating. |
| Gold deposit is too thick |
The gold has been plated above approximately 4 µm. As the deposit becomes thicker, tensile internal stress can become sufficient to pull the gold away from the surface, even when the surface was correctly prepared and activated. |
Keep the gold thickness at or below 4 µm where good adhesion is important. If the deposit has already peeled, remove the poorly adhered gold, prepare and reactivate the surface, and replate to a lower thickness. |
| Immersion deposit from contaminated process solution |
A very thin, sometimes virtually invisible, layer of another metal — most commonly copper — forms on the surface before gold plating. The gold may initially appear satisfactory but subsequently peels or rubs off because it is adhering to the poorly adherent immersion deposit rather than directly to the prepared surface. Copper contamination is particularly common when activators or cleaners have previously been used with copper or copper alloys. |
Replace the contaminated activator or cleaner, then prepare and reactivate the work before replating. Good housekeeping: do not process ferrous and non-ferrous metals in the same acidic activator, and replace cleaning solutions regularly. Avoid cathodic cleaning in cleaner that has previously been used with copper or copper alloys, particularly tarnished copper alloys. |
Deposit colour is wrong
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Gold deposit is too thin, allowing alloying with the underlying metal |
The colour is incorrect even though the gold is plating normally. This is particularly noticeable when plating directly over silver, where gold deposits up to approximately 0.2 µm can develop a greenish hue as the gold alloys with the underlying silver. |
Continue plating to increase the gold thickness. As the deposit becomes thicker, the influence of the underlying metal diminishes and the normal gold colour develops. |
| Gold solution contaminated with another metal |
The gold plates normally but develops an unexpected colour. Contamination can be introduced by a swab previously used with another plating solution and not thoroughly washed, or by a workpiece that has not been properly rinsed between processes. For example, copper contamination from a swab previously used with PP Copper can give the gold deposit a reddish or rose-gold hue. |
Prevent carry-over between processes. Thoroughly wash swabs with concentrated detergent and rinse very well with clean water before using them with another solution. Rinse the workpiece thoroughly between each process. If the Gold Brush solution has become significantly contaminated, replace it. |
| Incorrect electrode material |
The gold deposit develops an abnormal colour during plating. A copper electrode can contaminate the solution and produce a reddish gold deposit, while a nickel electrode can result in a noticeably paler gold colour. |
Use a suitable Platinum Electrode or Short Platinum Electrode. Alternatively, use a Carbon Electrode or Short Carbon Electrode. If the solution has become significantly contaminated by the incorrect electrode, replace the solution before continuing. |
| Gold coating is extremely thin |
At extremely low gold thicknesses, for example below approximately 0.005 µm, the colour of the underlying metal can influence the apparent colour of the finished surface. |
Continue plating to build a sufficiently thick gold deposit to develop the normal 24-karat gold colour. |
Poor coverage
|
Swab not fully wetted with plating solution |
Gold plates where good solution contact is made but fails or becomes weak elsewhere. The swab may look wet externally while not being fully saturated around the electrode. |
Fully saturate the swab with Gold Brush Plating Solution and keep it adequately wetted throughout plating. |
| Intermittent electrical contact |
Plating repeatedly starts and stops as the swab moves across the work. With a MultiPlater, the warning beep sounds and the indicator flashes between green and red as electrical contact is lost and restored. |
Check the workpiece connection and maintain continuous contact between the wetted swab and the workpiece while plating. |
| Swab too small for the area being plated |
Individual areas plate normally, but obtaining uniform coverage over the complete area is difficult or excessively slow. |
Use a larger swab appropriate to the area being plated. Use the Gold Brush calculator to select the appropriate swab and estimate the plating time. |
Speckled plating
|
Copper migration through the gold deposit |
The gold initially appears satisfactory but develops a speckled appearance after plating. This is most commonly seen when thicker gold coatings are plated directly over freshly plated copper, where the effect can develop within days. When gold is plated directly over copper or copper alloys, the same effect may take months or even years to become apparent. Copper atoms gradually migrate through the gold deposit and affect its appearance. |
Apply a suitable barrier layer between the copper-containing surface and the gold to prevent copper migration. |
Scratchy plating
|
Particulate contamination of the swab |
Fine scratches appear as the swab passes over the surface, particularly where retained particles are harder than the metal being plated. |
Replace the swab. Do not continue plating with a swab containing particulate contamination. |
| Swab stored alongside abrasives |
Scratching starts immediately with an otherwise apparently clean swab. |
Replace the swab and store plating swabs separately from abrasives, polishing compounds and other sources of particulate contamination. |
| Old silver-plating swab contains metallic silver particles |
An old silver swab has darkened or been exposed to light before being thoroughly washed, allowing retained silver compounds to be photoreduced to metallic silver particles. |
Replace the swab. Do not try to recover a swab once metallic silver particles are trapped in it. |
Incorrect plating thickness
|
Incorrect plating area estimated or calculated |
This is the most common cause of incorrect plating thickness. The actual area being plated differs from the area used to calculate the required plating time or coulombs. It is particularly easy to underestimate irregular shapes, edges, recesses or multiple surfaces. |
Estimate the total area being plated as accurately as possible and repeat the calculation using the corrected area. If you are unsure how to estimate the surface area of your workpiece, ask our Technical Assistant for help. |
| Thickness estimated from appearance |
The gold appears to have fully covered the surface, but subsequent thickness measurement shows that the deposit is thinner or thicker than required. Appearance alone is not a reliable indication of gold thickness once complete coverage has been obtained. |
Use the Gold Brush calculator to estimate the required plating time rather than judging thickness by appearance. Where a specified thickness is important, verify the result by XRF or deposited weight. |
| Plating conditions differ from those assumed by the calculator |
The calculated plating time has been followed but the measured thickness is consistently high or low. Swab movement, electrical contact, voltage and other practical factors can affect the actual deposition rate. |
For work where thickness is important, measure the resulting deposit by XRF or deposited weight and use the measured result to establish the actual plating performance under your working conditions. |
| Coulometer not calibrated to the actual process |
The required coulombs have been delivered but XRF or weight measurement consistently shows that the resulting thickness differs from the target. |
Calibrate the Gold Brush Coulometer calculator using an accurately measured deposit thickness or deposited weight, then use the resulting calibration factor for subsequent comparable work. |
