The basic elements that one needs to know are described here.
Working temperature
In order to achieve the best possible results, the working temperature of the respective electrolyte should be observed. These can be found in the instructions for the various products. Many electrolytes already work optimally at room temperature. Therefore, no external heating medium is required.
In general, it can be said that almost no electrolyte works well below 15°C, so it is important to pay attention to the temperature if you notice problems with the electrolyte. The temperature of the workpiece should also be taken into account - especially with pin plating.
Current density
In galvanic metal deposition, a certain ratio between current and electrode surface is particularly important. This is called current density. The current is specified in relation to the unit area and is expressed in A/dm². With the help of increased temperature and movement of the bath or the workpiece, higher current densities can be applied.
The cathodic current density is important for the quality of the coatings on the workpiece (cathode). For each electrolyte there is an optimal current density range within which the deposition is achieved with good results.
On the anode side, there is the anodic current density. This is particularly important for the stability of the electrolyte. As much metal should dissolve as is deposited at the cathode (workpiece).
Ideally, the anode dissolves as quickly as the metal is deposited at the cathode, so the electrolyte would last a particularly long time. In practice, however, there is a deviation.
For example, acidic zinc electrolytes are enriched faster than metal is deposited, which leads to turbidity of the electrolytes after a long time.
With nickel, on the other hand, the anode dissolves more slowly and the electrolyte slowly becomes poorer in nickel ions. In this case, suitable nickel salts could be added to increase the content again. However, nickel salts may not be sold freely because of the hazard classification. To improve the solubility of the anode and to reduce passivation, the manufacturer adds chloride ions to the electrolyte.
Anode material
As a rule, the metal of the specific electrolyte solution should be used as the anode material. For example, if it is a copper electrolyte, it is recommended to use a copper anode. The reason for this is that in the course of the electroplating process, the anode dissolves and the electrolyte solution is subsequently regenerated. This significantly increases the range of the electrolyte, as the metal is enriched again in the solution.
Attention:
Chromium is an exception. Chrome electrolytes (based on trivalent chromium) must not be used with chromium anodes, as highly toxic hexavalent chromium (chromium VI) can be produced! Furthermore, the electrolyte becomes unusable. Please use aluminium anodes. If you do not have an aluminium anode at hand, you can also use aluminium foil.
Incorrect anodes must be avoided at all costs, as they can contaminate the electrolyte and the electrolyte must then be discarded! In some cases, the electrolyte can be repaired by precipitation if the interfering metal precipitates faster than the electrolyte metal.
If no anodes are available from the electrolyte material, the use of inert anodes such as platinum or graphite is an option. In principle, care should be taken to ensure that only suitable anodes are used. If no attention is paid to this aspect, it is possible that the deposited layers will discolour or the electrolyte will be destroyed.
Caution: Before and after use, the anodes must be carefully cleaned. In addition, anodes that are not used should not remain in the electrolyte.
Expert tip:
With regard to graphite anodes, it is important to note that they are porous and that the components of the electrolyte may be absorbed. For this reason, different graphite anodes should be used for different electrolytes.
If you only want to use one graphite anode for everything, it is essential to soak the anode in water, at least two to three times for about 10 minutes. This will ensure that the components of the electrolyte absorbed by the anode are rinsed out. If you do not rinse the anode, it is possible that the substances will be released in the following electrolyte and that this will be contaminated.
Another disadvantage is that the resistance in the anode can rise sharply, making it unusable. Although graphite anodes can be used very universally, we do not recommend them because, although they do not chemically dissolve, particles enter the bath and cloud it due to the development of oxygen at the anode. As the process progresses, these particles are also deposited and the surface produced becomes darker. Therefore, metal anodes are to be preferred.
Alternatively, we can recommend platinised anodes, which are suitable for almost everything. However, you should not buy too cheap ones, sometimes the layer is too thin or incomplete and the underlying metal can contaminate the electrolyte.