Unlike in other sectors, where electroforming serves solely to coat, in the vinyl record industry, parts are produced that are then meant to be separated from one another.
The first step, that of separating the "metal master" from the silvered lacquer disc, does not require any special treatments. The thin layer of silver that covers the lacquer surface and the nickel that deposits on top of that layer form an alloy; consequently, when the "metal master" is detached from the lacquer, the layer of silver remains attached.
When electroforming from nickel to nickel, the part on which the electroforming is to take place must be pre-treated with a chemical substance. Without such treatment, the reduction from Ni²⁺ to Ni would create a bond that would make separation impossible, at least without damage.
Two commonly used methods include:
- solution of deionised water and a complex molecule (for example, albumin);
- solution of deionised water and a strong oxidising agent (for example, sodium dichromate). In this case, the upper layer of Ni(0) oxidises to Ni²⁺ through the following reaction:
This oxidising reaction requires numerous protons (H⁺) to occur, which is why it is facilitated by the presence of a strong acid, such as H₂SO₄.
Separation