The invention relates to a method in connection with steel production for handling of hydroxide sludge formed in the neutralization of spent metal-contaminated pickling agents from a pickling step for steel, preferably stainless steel and for using calcium fluoride in the hydroxide sludge to replace the natural fluorspar as a fluxing agent in connection with steel production. Accordingly, the addition of the reactive neutralization medium is monitored by the pH electrodes operated in continuous fashion, and the pH value is adjusted at the range between 9,0 and 9,5.