The iron/electrolyte interphase has been studied in the presence of NN-di(phosphonomethyl)glycine (DPMG) inhibitor with or without the bivalent cations. In electrochemical measurements, inhibition was assumed by the formation of a complex in the presence of DPMG. In situ atomic force microscopy provided direct insight into changes in the surface morphology at several hundred nanometres when topographical changes owing to the breakdown of the passive layer, and initiation of corrosion were monitored. Section analysis has revealed the degree of deterioration. Bivalent cations (Ba2+, Sr2+, Ca2+ and Zn2+) synergically improved the activity of DPMG, though the mechanism was different. Barium, strontium and calcium ions in blends hindered the anodic iron dissolution, while zinc ions influenced both the anodic and cathodic processes. Composition of the surface layer was analysed by X-ray photoelectron spectroscopy (XPS). The 2:1 Ba2+/Sr2+/Ca2+/DPMG molar ratio in the solution resulted in a surface layer with a composition of about 1.3:1 of cation/DPMG. In the case of Zn2+/DPMG mixture the surface layer was composed of a mixture of slightly soluble Zn2+/DPMG (similar to3:1) and zinc hydroxide.