09/10/2026
The secret to an excellent PVD coating starts with knowing your metal substrates: not all of them are suited to direct vacuum deposition. The reason is often outgassing, because however solid a metal may look, it is never truly “empty” inside: during casting, machining and storage it absorbs hydrogen, oxygen, nitrogen and water v***r. When we put it under vacuum and heat it, those gases are released.
The direct consequences: the vacuum degrades, pump-down times get longer, and oxides and impurities can end up in the film. This happens mostly with porous or die-cast materials, and with alloys containing high v***r pressure metals, such as zinc in brass.
At the other end are the metals that retain very little gas, which makes them the best performers under vacuum: stainless steel, OFHC copper, tungsten, and wrought (non-cast) aluminium alloys. Their dense structure and low dissolved gas content mean fast pump-down, a clean vacuum, and purer, more repeatable films. It’s no coincidence that vacuum chambers themselves are built from these materials.
For the problematic substrates, electroplating can be the starting point. A nickel or copper layer deposited in a bath seals the surface and acts as a barrier: the part entering the chamber no longer releases gas, and the PVD film grows on a stable base. Often the most robust route to a top-quality coating is to combine the two techniques and get the best of both.
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