Since many of the current chemicals used to remove iron rust are hazardous to the environment and human health, the combined use of a reducing agent and a biodegradable chelating agent has been suggested as an environmental friendly and highly safe alternative. In the present work, the compatibility of the newly devised cleaning test with a model iron rust stain was confirmed by X-ray diffraction and scanning electron microscopy. Additionally, the cleaning efficiency of the method was evaluated by X-ray fluorescence. The cleaning mechanism and the synergistic effect of the reducing agent and the chelating agent was investigated using the phenanthroline absorption measurement method, and the results revealed that the reduced iron ions were dissolved by the chelating agent. The cleaning test proved that tetrasodium 3-hydroxy-2,2'-iminodisuccinate (HIDS) is a promising biodegradable chelating agent as an alternative to ethylenediaminetetraacetic acid (EDTA) for removing iron rust. It was also confirmed that the type of reducing agent used determines the pH at which detergency is enhanced. The detergency of the combination of the reducing agent and the biodegradable chelating agent was equal to or higher than the detergency of the acid agent, and thus, it was concluded that the proposed method has a great potential for commercial use.
Keywords: chelating agent; cleaning; iron rust; reducing agent; synergistic effect.