Surface functionalisation by the introduction of self-healing properties into electroless Ni-P coatings

Ni-P∖alginate microgels coatings, as potential metallic protective coatings with self-healing properties, were deposited by the electroless method. The alginate microgels contained nickel chloride and sodium hypophosphite. It was proven that the reduction of nickel ions released from the microgels is possible on the steel and Ni-P coating surface. The self-healing effect of this system was studied by X-ray fluorescence (XRF), chronoamperometry and scanning vibrating electrode technique (SVET). An improved corrosion protection observed here is attributed to the reduction of nickel ions to metallic nickel on the tested surfaces. Differences in the surface concentration of nickel and phosphorous species in the corrosion tested coatings with and without microgels, as evaluated using X-ray Photoelectron Spectroscopy (XPS), provided substantial evidence for the formation of a Ni-P coating from the compounds included in the microgels.