Prevention of Sludge Generation in Sulfuric Acid Bath and Electrolytic Tin Plating by Sulfuric Acid Bath

Abstract

As for the electrolytic tinning bath used in tinplate manufacturing lines, the phenolsulfonic acid bath has been the mainstream in the world for many years. In recent years, some tinplate makers have applied the methanesulfonic acid bath. The author studied the sulfuric acid bath in order to develop a better plating bath. Although the problem of the sulfuric acid bath was sludge quantity caused by easy oxidation of stannous ion into stannic ion in the solution with the dissolved oxygen, it was found that only a small amount of sludge generated in the sulfuric acid bath in which specific phenolic antioxidants such as hydroquinone was added. The behavior of hydroquinone was discussed to be a radical scavenger. The tinplate obtained with the sulfuric acid bath stood comparison with that with the phenolsulfonic acid bath over a wide current density range.