The influence of glycine on the iron phosphorous alloy electrodeposition was investigated by electrochemical quartz microbalance (EQMB), in-situ external reflection FTIR spectroscopy, and electrochemical impedance spectroscopy (EIS) measurements. An increase of glycine concentration leads to a decrease of the iron-phosphorous alloy electrodeposition rate and an increase of hydrogen evolution. Strong adsorption of glycine species, such as H2(gly)þ, H(gly)± or/and Fe(gly)þ, have been observed during the hydrogen evolution and the Fe-P deposition reaction. Due to the concurrent hydrogen evolution the pH attains higher values at the interface than in the electrolyte bulk (pH2.5). The formation of adsorbed Fe(gly)þ and of the chelate complex Fe(gly)2 in solution avoids the precipitation of Fe(OH)2 in the pH range between 2.5 and ca. 7 at the interface. The phosphorous content of the iron phosphorous alloy deposit increases with the glycine concentration. This is due to a lower deposition rate of iron caused by the adsorption of Fe(gly)þ, while the hypophosphite reduction rate to phosphorous increases.

This is a post-peer-review, pre-copyedit version of an article published in Electrochim. Acta. The final authenticated version is available online at: https://doi.org/10.1016/j.electacta.2019.03.203. This study has partially received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 778357 and from European Social Fund, project No 09.3.3-LMT-K-712-08-0003 under grant agreement with the Research Council of Lithuania.