Kobe Steel, Ltd. has announced that it has completed development of hot dip galvanized (CG) steel sheet with no chromate layer and has begun commercial production.
The new steel sheet will replace the current chromate-treated CG steel sheet products. When production of chromate-treated CG sheet ends in March 2006, Kobe Steel will be the first Japanese steelmaker whose coated sheet products will be entirely chromate free.
The new CG sheet uses the Greencote GX-GC treatment, which coats an inorganic composite film on the galvanized layer of the steel. The coating contains no hexavalent chromium. The Greencote GX-GC steel is noted for its corrosion resistance, paintability and weldability, and has the same or higher properties than conventional chromate-treated steel. The sheet is used in construction, home appliances and office equipment.
Chromate treatment has been widely used for over 50 years as it improves the corrosion resistance and paintability of coated steel sheet. However, the EUfs RoHS (Restriction of Hazardous Substances in Electrical and Electronic Equipment) Directive bans the use of certain substances, including hexavalent chromium, from July 2006. Numerous industries have been undertaking measures to reduce the environmental burden, and an important issue has been to make coated steel sheet with no chromate layer.
In 1998, Kobe Steel became the first Japanese steelmaker to commercialize chromate-free electrogalvanized (EG) steel sheet called Zinkobella Greencote GX, noted for its high anti-fingerprint resistance, and has been switching over to this material. By the end of March 2005, it will cease production of chromate-treated EG steel sheet.