White Finishes: Layer Control And New Solutions For Intermediate Layers

Intermediate layers are returning to the center of electroplating design, especially in white finishes. The reason is both technical and economic: the reduction in thicknesses, driven by the cost of precious metals, has shifted attention from the final layer to the entire deposition system, making it necessary to optimize every stage of the process.

“In the case of non-precious alloy bases, the finish is built through a succession of layers. Intermediate layers determine both the aesthetic outcome and wear resistance, particularly with regard to corrosion and tarnish phenomena. The critical point is the interaction between different metals. If they have distant redox potentials, a behavior similar to a galvanic system is triggered: one oxidizes, the other reduces. The surface, over time, is affected” explains Fulvio Sinisi, R&D & Technical Manager of the Surface Treatment division at Legor, a leading company in the production of metal alloys and electroplating solutions for the jewelry and fashion industries.

The strike is therefore necessary: it is a very thin layer with a barrier and adhesion function. It helps limit the migration of base metals toward the surface and creates a stable condition for the growth of the next layer. In operational terms, it is a primer: it makes compatible materials that, in direct contact, would cause adhesion or stability issues.

“In palladium-based white finishes, deposition on bronze, used as an intermediate layer or as an electroplating base, presents adhesion issues, which makes it necessary to insert a strike between bronze and palladium. Historically, this step was solved with a gold strike: even when not specified in the technical requirements, it was still applied to avoid defects over time. Legor proposes an innovative solution: the PDSTARK-ST bath allows a thin layer of palladium to be deposited directly onto bronze, improving the adhesion of the final layer and stabilizing the system.”

The advantage is twofold. On one hand, an expensive metal and a complex operational step are eliminated. On the other, a material continuity is achieved: the final palladium grows on a compatible layer, increasing overall adhesion. This step also impacts the coating composition. The palladium used in the strike contributes to the total percentage present in the finish, becoming an integral part of the final result rather than just a hidden technical element.

The critical issue? The bronze layer: the quality of the electroplated deposit must be consistent in composition and distribution across the entire surface; otherwise, subsequent layers inherit discontinuities that compromise adhesion, color, and long-term stability.

Legor also has a solution for this, with “The VEGA process, which acts on this level, allowing control of the composition of the deposited alloy and keeping it stable over time. Bronze baths, by their very nature, are unstable: throughout their lifecycle they change behavior, with variations that directly affect deposit performance. Even in the longest-lasting cases, which can reach up to one year, a deviation between the beginning and the end of the bath life is observed. With VEGA, the stability of white bronze thus becomes a verifiable condition on which subsequent layers can be built,” concludes Sinisi.

The construction of the finish thus returns to being a controlled system, where each layer has a precise and verifiable function. From the stability of white bronze to the palladium strike and the final layer, quality is no longer entrusted to a single step but to the coherence of the entire process. It is on this continuity that the aesthetic and technical durability of surfaces is now based.