After the object has been cleaned as described in the first pre-treatment, proceed with electrolytic cleaning (degreasing) using either a commercial preparation or a caustic soda bath — sodium hydroxide (NaOH) at 35 g per liter of water.
A highly effective and safer alternative, producing fewer fumes and easier to handle, is the following mixture:
– 15 g/L caustic soda (NaOH)
– 45 g/L trisodium phosphate (TSP, Na₃PO₄·12H₂O)
Alternatively, TSP can be replaced by trisodium citrate (Na₃C₆H₅O₇) in the same proportions — this version is more environmentally friendly
Use only high-purity chemicals to avoid impurities that may cause inconsistent results.
Before starting the electrolytic degreasing, stir the solution thoroughly to ensure uniform composition and conductivity so that current flows evenly.
When preparing a new bath, it should be used only after one hour, allowing chemical reactions with water to stabilize; otherwise, the items may develop current burns or dull patches.
Operating Conditions
-
Temperature: Room temperature
-
Voltage / Current: The current density should be 1 ampere (A) per 10 cm² of surface area
(e.g., a 70 cm² surface → 7 A).
Measure current using a clamp ammeter at the cathode (-).
With our standard parameters:
Cables: Use multi-stranded copper wires.
Copper conductor diameter (bare) at least 2.5 mm — corresponding to 4.9 mm² cross-sectional area — to safely carry up to 15 A.
Always turn on and adjust the power supply before immersing the items in the degreasing bath (as in all plating baths).
If the items are immersed without current, they oxidize immediately.
Duration: 3–5 minutes.
For double plating, perform a second degreasing (1 minute) after the underlayer.
This step removes any weakly bonded areas from the first layer, ensuring perfect adhesion.
Anode:
Use a stainless-steel sheet, ideally type 316 or 304, with a minimum thickness of 1.5 mm and surface area of at least 5 × 10 cm per liter of bath.
If the anode is too thin, part of the current converts to heat (resistance), noticeable when the anode or cable ends become warm — which should not occur.
Clean the anode after each use (impurities tend to accumulate there). Replace the bath frequently.
Degreasing Container:
Use polypropylene (PP) or high-density polyethylene (HDPE) containers.
Glass is unsuitable because many alkalis corrode it (though it is appropriate for acidic neutralization baths and water rinses).
HDPE deionized-water containers are ideal for this purpose and can be repurposed.