Hollow mesoporous silica nanoparticles loaded with phosphomolybdate as smart anticorrosive pigment

Recent developments in surface science and technology open up new opportunities for the development of smart pigments through the integration of nanoscale containers loaded with active components into coatings. Regarding the external factor to trigger the inhibitor release, a change in pH is a very interesting stimulus since corrosion activity leads to local changes in pH. Although several types of nanocontainers and encapsulation approaches have been proposed and studied to meet this goal, mesoporous silica nanoparticles (MSNs) are especially interesting as they retain their solid properties as long as pH of the surrounding medium does not exceed ~11. On the other hand, the use of hollow mesoporous silica nanoparticles (HMSNs) with a large cavity inside each original mesoporous silica nanoparticle has recently gained increasing interest due to the higher loading capacity. In the present work, an environmentally friendly corrosion inhibitor with good anticorrosive behavior when applied on steel substrates, sodium phosphomolybdate, has been successfully loaded and encapsulated on HMSNs. The pH-dependent release of the corrosion inhibitor from the loaded/encapsulated HMSNs has been confirmed. In addition, an improved anticorrosive behavior of the coatings formulated with loaded/encapsulated HMSNs has been observed by Scanning Kelvin Probe (SKP).