Winner of the Innovation of the Year Steelie Award 2022
In AC electrolytic pickling, scale removal and dissolution of the chromium-depleted layer can be improved by more than 1.4 times (vs DC electrolytic pickling) by suppressing the formation of the passivation film achieved through continuous AC polarity change and by accelerating the dissolution reaction in the sulfuric acid tank.
It is important to note that this AC electrolytic pickling technology is applied to 4 feet of coil width, the world’s widest width to which this process is administered. Hence, the world’s first high-speed extended-width AC electrolytic pickling technology was commercialised with notable benefits observed in productivity, quality, cost and environmental impact.
Firstly, on-site commercial application of AC electrolytic pickling enhances pickling performance, removing the need for additional defect elimination processes and facilities.
Moreover, because the pickling process is often identified as a major bottleneck in the hot annealing and pickling (HAP) line stages, the observed benefits translate directly into increased production volume and reduced cost. Because ancillary manufacturing process facilities, such as coil grinding lines, can be omitted, lead time is shortened, cost reduced (50%), and productivity enhanced (13.1% at a minimum).
Secondly, surface gloss and roughness are far superior to chemical pickling output. Enhanced pickling performance and the simplification of mechanical pickling methods have significantly improved product quality, giving rise to new high-grade STS products.
Thirdly, although simple in concept, AC electrolytic pickling technology offers a powerful solution to cut (by 26%) the consumption of nitric acid, which generates NOx.
Because NOx is a source of environmental degradation, any abatement of nitric acid in the manufacturing process positively impacts the environment.
Finally, applying this promising technology can be expanded even to the carbon steel industry, yielding instant benefits to both steelmakers and their clients.