The Anticorrosive Mechanism of Marine Organic Coating

Ships serving in the Marine environment are faced with serious corrosion problems due to the role and influence of complex ocean medium and harsh climate environment. As a result of multiple corrosion effects, the ship structure strength and propeller propulsion efficiency decreased, maneuvering performance deteriorated, the noise increased, sonar interfered, and the instrument sensitivity decreased and even failed.

All of the above problems not only shorten the service life of the ship, reduce the navigation rate, but also increase the resistance and significantly increase fuel consumption. Moreover, the leading-in repainting for corrosion will cost a huge amount of maintenance and repair. The application of the high-performance anticorrosion coating is a simple and effective method to prevent corrosion of metal materials and prolong their service life. Marine high-performance anticorrosive coatings have been a hot spot in Marine materials research at home and abroad, and also a key technical field of Marine power development. The anticorrosion effect of organic coating mainly has the following 4 aspects.

Shielding effect

The shielding effect of organic coating is applied to the metal surface, which makes the electrolyte (water, oxygen, chlorine, etc.) cannot contact with the metal interface directly, thus preventing or slowing the electrochemical corrosion of the metal. The shielding effectiveness is closely related to the anti-electrolyte permeability and thickness of organic coatings.

Organic Coating

Wet adhesion

Due to the influence of solvent volatilization or preparation process, the organic coating always has defects such as pores, which become the main channel of electrolyte infiltration. It is found that the permeation and oxygen rate of organic coating is higher than that of iron and steel corrosion, so the protective effect of organic coating is not only shielding.

The wet adhesion between coating and steel surface plays an important role in corrosion prevention. Wet adhesion refers to the adhesion in the presence of water, which ensures that water and oxygen cannot rapidly diffuse on the metal surface and thus slow down metal corrosion.

Filler corrosion inhibition

In the presence of water, anti-rust pigments in the paint will release corrosion ions and inhibit the process of metal corrosion.

The cathodic protection of the sacrificial anode

Active metallic powders (such as zinc powders) in coatings can also act as sacrificial anodes, protecting the cathode metal matrix.

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