Description
Since 1750 when Rinman, in Sweden, first proposed “soaking steel for one or two months in pyroligneous acid” to remove scale, we have progressed through hydrochloric, sulphuric, mixed acids, molten salts and electrolytic methods to our present procedures of scale removal. This paper will review the past and present state of the art, available equipment and some of the methods of removal or recycling of the effluents.