Some time ago and partly still today, to obtain the appearance of the colour rose gold, the base material must be dipped in a mixture of gold and copper.
Involving gold is an expensive process, and even a small deviation in the gold and copper mixture could result in a completely different colour appearance, meaning different “L*’, “a*” and “b*” values.
Such a dipping process is very costly.
Every re-coating needs de-coating which subsequently results in the loss of the expensive raw material Gold.
Recently PVD - Physical Vapour Deposition - offers an excellent rose gold colour based either on sputtered Titanium / Zirconium or arc-evaporated in nitrogen and acetylene atmosphere.
Three problems that occur to PVD Coating companies aiming for rose gold
1. Adhesion on shiny parts
2. Non-uniformity over broad range
3. Conformal colour coverage on complex 3-D parts like faucet parts or chandeliers
1. Enhanced voltage equipped controller
2. Trimetallic target
3. Arc based plasma beam etching on materials
By using bi-metal or tri-metal alloy – high uniformity (same colour coordinates) can be obtained over large areas and a stable appearance for prolonged time.
In principle, the eutectic point is moved by addition of materials and bonds the majority of Ti or Zr atoms with high degree of carbon and nitrogen.
With Titanium and Nitrogen, though few companies can achieve 1:1 ratio of anion to cation, bonding of carbide anion and titanium cation has always been a challenge.
Alloyed cathodes improve the processes by systematic transformation of phase with ternary eutectic points.
Albeit all these improvements in auxiliaries, a process engineer should take intense care by choosing
- the right cleaning process
- cleaning of substrates by appropriate chemicals
- intense etching processes for subsurface nano-cleaning
- the coating machine configuration
- modified power supply design
to achieve high intense and uniform plasma over a broad coating range of 1.5m.
Uniform and conformal coating with rose gold appearance can be obtained either through cathodic or sputtering process.
Customers achieve higher deposition rates and higher smoothness for rose gold coating by using an arc-assisted sputtering process. The combination of both coating processes excels the strength of either individual process with respect to coating speed and surface quality.
Potentials to optimize your process:
Use of the best coating materials and the right target materials for deposits
excellent electrical controllers that produce intense and optimized plasma conditions with right electron- and gas-temperatures for optimal chemical kinetics
a machine design which ensures precise plasma flow.
A successful coating of rose gold colour with high uniformity and reproducibility is challenging but certainly achievable with special auxiliaries and alloyed target materials.