There are two basic forms of micro-capsules, 1st form is covered by one shell made of urea-formaldehyde, while the 2nd one is covered by two shells (first one is urea-formaldehyde and the second one made of poly-urethane).
Both forms are filled with two types of corrosion inhibitor (corr A and the other is corr B). Many tests are performed; Optical microscope scanning was applied to the micro-capsules in order to confirm the formation of capsules. Micro-capsules were weighed in order to measure the shrinking rate under heating of the micro-capsules. Infra-red spectroscopy was applied to make sure of the formation of shells of the micro-capsules. Physical properties were monitored weekly to confirm the stability of the micro-capsules. The purpose of preparing theses micro-capsules is to install a system of self-healing paints for corrosion protection.