Abstract: A method is provided for zincating aluminum substrates for metal plating thereon wherein the plated aluminum product has smoothness, dimensional integrity and increased production yield of the plated products. The substrates also have enhanced paramagnetic thermal stability of ENP coatings used on memory disk products. A zincate bath contains as additives Fe.sup.+3 and NaNO.sub.3, and a chelator to chelate the iron, with a preferred iron chelator being Rochelle Salt and with the amount of Fe.sup.+3 being controlled at a preferred concentration of 0.2 to 0.3 g/l. A preferred zincating method employs an etchant composition comprising HNO.sub.3, H.sub.2 S0.sub.4 and H.sub.3 PO.sub.4 to etch the aluminum substrate prior to zincating. Use of this etchant composition, either alone or with the zincate bath of the invention, is particularly effective for aluminum substrates which have been ground to a smoothness of less than 100 .ANG..

Abstract: A method is provided for producing paramagnetic electroless nickel-phosphorus (ENP) coatings on zincated aluminum substrates using an ENP bath containing antimony and/or cadmium ions and/or an adjusting operating pH, which coated substrates have enhanced retention of their paramagnetic properties after being exposed to elevated temperatures on the order of 310.degree. C. as, for example, when the ENP coated substrate is further treated by sputtering operations to form another metal layer on the coated substrate to produce magnetic memory disks.

Abstract: A method for producing smooth metal coatings on zincated aluminum substrates using a specially formulated zincating bath containing an additive comprising a bath soluble cationic condensation polymer represented by the general formula: ##STR1## wherein: Z represents a group of atoms necessary to complete a heterocylic compound having a five or six membered ring containing at least 2 nitrogen atoms;R is nothing or the alkyl group of an alkylating agent;X is Cl, Br or I, andn is >1.

Abstract: A method for producing extremely smooth metal coatings on zincated aluminum substrates using a special double zincating procedure and/or a specially formulated electroless metal plating bath employing a unique plating process.