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PRODUCTS FINISHING — PFonline.com 15 can crumble when the power is restored. Lead chromate sludge poses a health risk. Disposing of this is time- consuming and expensive. • Handling lead c hromate sludge is very dubious from a work safety point of view. Therefore, it requires appro- priately high levels of protective measures. Dimensionally Stable Anodes Dimensionally stable anodes are an interesting alternative for hard chrome plating (see Figure 2), with a platinum surface on titanium or niobium as the base substrate. Platinum-plated anodes offer many benefits in hard chrome plating. This includes the following benefits, among others: • Pr ocesses with dimensionally stable anodes are almost completely free of lead and therefore considerably more environmentally friendly. The result: no lead chromate, fewer health risks for workers and no disposal costs. • Pr oduction downtime and exchanges are not required, as with lead systems. • Pt/Ti and Pt/Nb anodes normally do not change their shape within the usual three-year period of use. • The layer thicknesses on the cathodic compo- nents are even. Mechanical reworking is unnecessary. • The amount of ener gy required is considerably lower than with lead anodes. In the long term, the voltage difference (e.g. change = around -1V with Pt/Ti anodes) means significantly lower costs. The reason for this is the anodic oxygen surge, which is much higher with lead than with platinum. • Components such as power supply carriers and frame structures made from CuTi can be reused several times. This means that the time taken for the method to pay off is drastically lower when compared with lead anodes. • Leftover platinum recovered at the end of the re-coating means that some original precious metal costs are recovered. To achieve perfect results, adapt anodes to the construction of components to be coated. This makes dimensionally stable anodes possible (plates, cylinders, T-shapes and U-shapes), whereas lead anodes are mostly standardized sheets or rods. Pt/Ti and Pt/Nb anodes don't have a closed surface, but are expanded metal sheets with variable mesh sizes. This leads to good power distribution; the electric field can work in and around the mesh (see Figure 3). In coordination with the client, further optimizations can be carried out: • To maximize the separation conditions in the electro- lyte, an optimized mesh size is used (see Figure 4 and Table 1). • This enables better gas removal as well as stronger elec- trolyte movement because of turbulent flow in the mesh. Fig. 1: Lead anodes usually deform relatively quickly in the electrolyte. Fig. 2: Platinum/titanium anodes coated using high- temperature electrolysis retain their shape over a long period of time. Fig. 3: Pt/Ti anodes made from expanded metal grids. The expanded metal mesh allows optimal electrolyte movement. The distances between the anode and the cathodic component can be reduced, and the current density increased. The result: better quality in a shorter time. To achieve perfect results, adapt anodes to the construction of components to be coated. TITANIUM VS. LEAD ANODES