The mechanisms proposed to explain ACD electroless Ni-P deposition are re-examined and the most important features underlined. Oxidation of hypophosphite on the Ni-P surface is recognized as the rate determining step of the process. The possibility of a bridged intermediate with hypophosphite and hydrolyzed nickel adsorbed at the surface is examined and proved feasible by quantum mechanical calculations. A comparison of electrodeposition and ACD electroless deposition shows that the two processes are anti-correlated, ACD being directly related to the electrolytic hydrogen discharge. Addition of other elements can greatly influence ACD electroless NiP plating process. Metals giving anomalous alloy electrodeposition, such as Zn, Co and Fe behave normally in electroless baths. Elements electrodeposited by induction, such as W and Mo, decrease the P content and the deposition rate. A similar effect occurs for Re, Ce and Cu. Some of the metal stabilizers have also a brightening effect on NiP deposits. This is the case of Cd, Bi, Te and Cu and brightening is related to their interaction with adsorbed hydrogen, stabilized by these additives. (C) 2013 Elsevier Ltd. All rights reserved.