Challenge in Zinc-Chromate Passivation Waste Management at Borçelik’s Galvanizing Line

Challenge in Zinc-Chromate Passivation Waste Management at Borçelik’s Galvanizing Line

In Borçelik’s galvanizing lines, a passivation chemical is applied to enhance the corrosion resistance of zinc-coated steel surfaces. This process partially dissolves loosely bound zinc residues and forms a thin chromium-based protective layer. Over time, the acidic passivation solution becomes saturated with dissolved zinc and chromium, rendering it unusable and transforming it into hazardous waste & wastewater.

Treating this waste is difficult using conventional wastewater treatment methods, which are typically slow and inefficient. While alternative technologies such as vacuum evaporation exist, they require high energy input and are not always feasible for large-scale applications.

Borçelik generates approximately 300 tons of this wastewater annually. Its low pH demands the use of large quantities of alkaline chemicals for neutralization, resulting in significant sludge production. The waste contains high concentrations of dissolved zinc and chromium (above 1 g/L), along with trace amounts of other metals. Since each metal requires a different pH level for effective chemical precipitation, the conventional treatment plant—primarily optimized for iron removal—cannot efficiently precipitate all of the chromium and zinc present in the waste stream.

Borçelik is actively seeking partners to co-develop or test solutions that address this challenge by:

·       Regenerating and reusing the passivation chemical, or

·       Treating the waste stream using lower-energy and faster methods than conventional or energy-intensive approaches.

The objective is to reduce the environmental impact, operational costs, and sludge volume associated with current practices. Borçelik is open to collaboration at pilot or demonstration scale and welcomes innovative proposals from industrial or research stakeholders.