In line with electrochemical processes, organic bath additives are oxidised on the active layer of the anode (figure 1). The additive consumption and the associated supplementary costs increase. The oxidation products which emerge contaminate and partially destroy the functionality of the baths – a short bath life cycle is the result.
The shielded anode can be one solution – a special anode developed by METAKEM.
Schematically (figure 2) it consists of a base material, one active layer as well as the shielding. The base material is usually titanium, the active layer consists of a mixed oxide layer or platinum. The shield is a grid structure directly connected to the anode made of fine plastic and/or titanium.
The shielding has a positive effect on the occurances on the anode and offers advantages:
- Reduction of the additive consumption by means of a mechanical barrier
- Formation of a potential wall (in case of conducting grid structure)
- Cost saving compared to membrane box application
- Quick interchangeability and no maintenance
- Recoating possible, with reusability of the shielding
Figure 3 shows the use of a shielded anode in a copper bath of the printed circuit board industry – here the additive consumption was reduced to the half in reverse pulse plating and to one third in direct current.
Apart from dimensionally stable anodes, metal sheets and expanded metals made of nickel, soluble anodes, and titanium anode baskets are also generally shielded.
Product information on request.