The German specialist finishing company Oberflächentechnik Döbeln GmbH has been working successfully with a hexavalent-chrome-free coating process for over a year. The trivalent chrome electrolyte (SurTec 883) is used for chrome plating in shades of white. For almost 20 years, Oberflächentechnik Döbeln GmbH has specialised in applying metallic coatings using electroplating processes, together with the accompanying pre-treatment and posttreatment phases.
The company’s 50 employees electroplate components for a variety of industries in its six fully automated machines. Four of these are responsible for decorative chrome plating, which includes coating fixtures and fittings for use in shops, kitchens and bathrooms. The company has now coated 125,349 square metres of substrate using the new generation trivalent chrome process, which is an area equivalent to around 18 football pitches.
SurTec has many years’ experience of trivalent chrome electrolytes and is an approved supplier of trivalent chrome coatings to Japanese and French OEMs. An audit of the machines at the Oberflächentechnik Döbeln site was carried out and the company modified its equipment according to the recommendations in the audit. The conversion costs amounted to around 100,000 euros.
When production with the new electrolytes began, the managing directors of Oberflächentechnik Döbeln GmbH set themselves a number of objectives. The appearance of the coating had to be similar to that of hexavalent chrome and it was essential to prevent yellowing. At the same time, the machines needed to be 100% available for seven days a week over three shifts. Other goals included a maximum cycle time of seven minutes and a coating thickness between 0.1 and 0.3 μm.
Close to the colour of hexavalent chrome
After over a year of production using the new system, the results are positive. The colour of the coating is stable and very close to that of hexavalent chrome, as shown by colour measurements using a Konica Minolta d 700 after 13 months of production:
SurTec 883: L = 82.20 / a = -0.42 / b = 0.06
Hexavalent chrome: L = 80 to 84 / a = -0.5 to -1 / b = -0.5 to -1.4
A much larger area can now be electroplated per 10,000 Ah than was previously the case. The new process can coat up to 430 m² compared with 100 to 200 m² with the old one. A single-sided coating with mixed oxide is also possible. The company has achieved its original objectives of seven-day-a-week availability in threeshift operation, together with current densities of 3.5 to 5.0 A/dm² and coating thicknesses between 0.1 μm and 0.3 μm within four minutes.返回概览
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