Electroplating / Chromium plating
Pragogal Cr 870
low concentration chromium plating bath
The Pragogal Cr 870 process represents an up-to-date low concentration chromium plating bath on the basis of two liquid catalysts, Pragogal Cr 871 and Pragogal Cr 872. The catalysts-based way of chromium plating enables easy deposition of a very bright decorative chromium coatings within a broad range of current densities. The bath is running within a wide range of chromic acid concentrations 150 – 250 g/litre without any other acids and other detrimental substances and, therefore, the bath maintenance is quite easy. The bath composition and advanced system of the catalysts facilitate the direct deposition of a decorative coating on copper and its alloys without any significant dissolution of the substrate.
The needed refilling amount of the catalysts Pragogal Cr 871 and Pragogal Cr 872 respectively is usually directly proportional to that of chromium trioxide. It should be refilled with both 50 – 60 millilitres of Pragogal Cr 871 and 60 millilitres of Pragogal Cr 872 respectively
The inividual bath components for 100 litres bath capacity should be as follows:
| Component | Optimum | Recommended range |
| Chromium trioxide | 20 kg | 15,0 - 35,0 kg |
| Pragogal Cr 871 | 0,2 - 1,5 l it dependes on the bath temperature, higher concertation of the agents is necessary when higher bath temperature is used at temperature interval 32 - 40 °C 5 - 10 ml Pragogal Cr 871 is added |
|
| Pragogal Cr 872 | 1,5 l | |
| Pragogal Cr 892 | 20 - 100 ml na 100 l lázně podle potřeby (smáčedlo) |
Operating conditions and parametres of the bath:
| Cathodic current density | 5 - 30 A/dm2 |
|---|---|
| Anodic current density | 1 - 10 A/dm2 |
| Voltage | 5 - 10 V |
| Bath temperature | 35 - 40 °C |
| Density of the bath | 19 °Bé at 210 g/l CrO3 |
| Current output | 18 - 25 % |
| Material of the anodes | PbSn (6-7 % Sn) or, preferably PbSnAg (6-7 % Sn and 0,5 % Ag) |
| Surface of the anodes | At least of twofold surface area of the parts to be plated |
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