COMPOSITION AND PROCESS FOR THE CHEMICAL CONVERSION OF METALLIC SUBSTRATES

摘要

Acid solution for the chemical conversion of metallic substrates, comprising: a polyphosphate, soluble in water and of the formula (X PO3)n in which n>/=3 and in which X is an alkali, alkaline earth metal or ammonium, an organic chelating agent and the zinc iron, the pH being brought to the desired value by means of an inorganic acid selected from the group comprising sulphuric hydrochloric and nitric acid.