GB1061950A - Iron plating bath liquids and methods - Google Patents

Abstract

Electroplating with iron is effected from an acid aqueous solution containing a ferrous salt and, as a dispersant for ferric hydroxide, a condensation product including the grouping A-R-A1-SO3 where R is a methylene radical or a straight or branched chain aliphatic nucleus and A and A1 are like or different aromatic groups each containing a naphthalene nucleus joined to R. Typically the ferrous salt is the chloride and the condensation product used is the sodium salt of the product formed by condensation under acid conditions of a b -naphthalene-mono-sulphonic acid and formaldehyde present in a 2:1 molar ratio and is used in the plating bath at a concentration of 0.25 to 1 g/l. The bath contains a small amount of free hydrochloric acid and examples are given in which the ferrous chloride content is 187 or 454 g/l. Aluminium pistons for I.C. engines may be plated with hard iron layers by first etching in a nitric acid-hydrofluoric acid bath, then zinc plating by immersion, rinsing, electroplating with copper from a cyanide bath, rinsing, dipping in dilute hydrochloric acid, and then immersing with the current on into the iron plating bath at a temperature of 60 to 71 DEG C. and employing a cathode current density of 100 to 125 amps/ft2. An outer layer of tin may then be electroplated from a stannate tin bath containing free potassium hydroxide. Reference is made to producing soft iron electrodeposits at bath temperatures of 82 to 88 DEG C.