Studies of Li depletion in sections of Li 2 CO 3 -primer comprising a polyurethane binder, MgO, TiO 2 , BaSO 4 in addition to Li 2 CO 3, were performed using a combination of particle induced γ-ray and X-ray emission spectroscopies along with SEM/EDS analysis. A mixture of depletion behaviours were observed. At the earliest stages (to around 48 hours) initial release was confined to the surface. At longer times (168 hours) voids developed deeper into the primer and after 500 hours Li 2 CO 3 dissolution was observed at places throughout the thickness of the primer to the metal/primer interface. Microscopic transport pathways formed which involved all large inorganic particles. SEM showed that rupture of the polyurethane matrix contributed to network formation. Finite element analysis indicated that rupture may be due to internal stresses around particles isolated in the polyurethane matrix and associated with water uptake. Thus the transport network seemed to be generated by chemical dissolution at the particle/polymer interface and may be enhanced by mechanical degradation due to internal mechanical stresses. The release kinetics of Li 2 CO 3 inhibitor from the primer was followed as a function of time and the data analysed according to a release behaviour of t n . There was very rapid initial release of Li followed by a slower release of Mg and to a lesser extent Ba. The value of n varied significant with time, but showed a mixture of Fickian release and direct dissolution for Mg and Ba at intermediate times, but transport through a pore network at longer times. The leaching data was interpreted in terms of local transport networks that developed in the primer with time.

Polyurethane coatings have been the focus of continuous innovation, such as bio‐based coatings and self‐healing coatings. This study investigates the route achieving superior coatings by in situ integration of pongamia oil during the curing process. Stronger urethane and carbonyl bonds for these oil‐modified coatings are observed using Fourier transform infra‐red spectroscopy. Thermogravimetric analysis reveals an increase in their thermal stability. A sustained high coating resistance and an increased Bode impedance (by ∼102 Ω cm2) for the oil‐modified coatings is observed using electrochemical impedance spectroscopy, which is corroborated by the cyclic corrosion test. Scanning electron microscopy depicts a roughened coating morphology with an increased water contact angle due to the integrated oil‐polyurethane polymer chains. Further, a preliminary computational fluid dynamics confirms this inhibited electrolyte mass flow through an oil‐modified coating with denser regions as compared to a clear coating. A consolidated schematic model incorporating the experimental and simulation results is proposed.

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