The cathodic protection provided by epoxy coating/epoxy zinc-rich coatings on defective areas under atmospheric and immersion conditions was studied via a Q235 wire beam electrode (WBE), scanning electron microscopy, X-ray diffraction, and surface morphology analysis. The results showed that the cathodic protection processes under the two test conditions displayed significant differences. The effective protection time of the defective area under the atmospheric condition was 1.7 times that under the immersion condition. Compared with the immersion condition, zinc particles in zinc-rich coatings under the atmospheric condition exhibited higher cathodic protection efficiency. The possible activation mechanism of zinc particles under the two conditions was elucidated.

Self-healing coatings formulated by stimuli-responsive container technology are regarded as a prospective strategy for long-term corrosion protection. However, such types of coatings suffer from low coating adaptability and delays in corrosion protection because the occurrence of corrosion is prior to the release of healants from containers. Herein, we took advantage of the easy hydrolysis of MOF-199 for water-induced self-healing properties. Mixed corrosion inhibitors were loaded into MOF-199 and then incorporated into acrylic coating. The water sensitivity of MOF-199 was investigated and EIS tests were used to evaluate the self-healing performance. Due to the collapse of the porous MOF-199 structure, corrosion inhibitors could be released from MOF-199 with the invasion of water into acrylic coating. The corrosion resistance performance of damaged self-healing coating gradually increased. The metal exposed to artificial defects was well protected due to a barrier formed by corrosion inhibitors. Owing to these merits, this self-healing coating is recommended for use in various fields of engineering for corrosion resistance.

Corrosion in the interface zone is a complicated local corrosion phenomenon. The conventional single-electrode method finds it difficult to obtain the kinetic information of corrosion occurrence and development process. In this paper, metal corrosion was studied by Wire Beam Electrode (WBE) technology on the interfaces of sea mud/seawater and seawater/atmosphere. The study found that the metal corrosion in the interface is a process of coupling a dual corrosion cell into a single corrosion cell. Initially, a corrosion cell is formed with the seawater/atmosphere interface acting as the cathode and the upper part of the metal in the seawater area as the anode. This is due to the oxygen concentration cell caused by the waterline effect. The cathode area is always enriched near the seawater/atmosphere interface. The lower part of the metal in the seawater area and the metal in the sea mud area are the anode and the cathode, respectively, of another corrosion cell. Along with the immersion time, the anodic area of the first corrosion cell gradually extends to the lower part of the metal in the seawater zone and finally the sea mud zone, resulting in the disappearance of the second corrosion cell. In the single corrosion cell stage, the seawater/atmosphere interface is the cathode area; the seawater area and the sea mud area are the anode areas, and the electrode adjacent to the cathode area becomes the anode area with the largest current density. During the whole experiment, the sea mud zone is a process of polarity transition from the cathode zone to the anode zone, and finally forms the anode zone of the whole electrode together with the anode zone in the sea zone.