Smart acrylic coatings for corrosion detection

•Acrylic polymers modified with 5-acrylamido-1,10-phenanthroline (AMP) were synthesized and characterized.•Modified polymer forms complex with Fe2+ ions released during corrosion and shows red color at corrosion sites.•Polarization resistance and color change of coating were correlated to optimize AMP content of the polymer.•Modified polymer detects the onset of corrosion at an early stage.•Polymer has shown its potential to be used as binder for corrosion sensing coating. Corrosion detecting coating was prepared using acrylic polymer chemically modified with 5-acrylamido-1,10-phenanthroline (AMP). Modified polymers having varied AMP content were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetric (DSC) and thermo gravimetric (TGA) analysis. The modified polymer after complex formation with Fe2+ ions showed additional absorption peak at 359nm in UV–vis spectrum confirming the polymer-Fe (II) complex formation. Corrosion sensing ability of these polymers was evaluated by immersing the coated mild steel panels in 3.5% NaCl solution and visually monitoring the color change of coating. Electrochemical impedance spectroscopy (EIS) was used to measure the polarization resistance (RPR) of coated steel specimens and correlated with the color change of coating. Coating from the point of color change was removed and bare metal was analyzed by scanning electron microscopy (SEM) to reconfirm that the point of color change was the corrosion site. Results reveal that these new sets of polymers can be used for corrosion detection.