Metal corrosion

Metal corrosion is one of the major problems facing countries, which in addition to annual costs and material losses, also causes environmental problems.

Several solutions have been adopted to combat the phenomenon of corrosion, one of the most widely used methods is the use of corrosion-protective polymer coatings.

These coatings increase the lifespan of the structure by creating a physical barrier against the penetration of water and corrosive agents.

However, over time, due to the penetration of corrosive agents through the pores, the coating is damaged and its durability is reduced.

To solve this problem, the use of anti-corrosion pigments has been proposed. Today, with the development of nanoscience,

the production and use of anti-corrosion nano-pigments has been considered.

In this chapter, we will first briefly discuss corrosion, coating, and nano-coatings, and

by creating a bridge between these concepts, we will become more familiar with the research conducted.

Basic concepts of metal corrosion

Corrosion is a process that causes the destruction of metals. The most common example of corrosion is the rusting of steel.

Most corrosion processes are electrochemical in nature, involving two reactions on the metal surface.

One of these reactions is oxidation (decomposition of iron), which is associated with the anodic part of the reaction.

The second reaction is reduction or reduction (i.e. reduction of oxygen), which is associated with the cathodic part of the reaction.

The products of electrochemical reactions react with each other non-electrochemically

2 Fe + 2 H2O + O2  2 Fe(OH)2      (1-1)

Types of Corrosion

Steel is a widely used engineering material in industry, used in manufacturing, construction, defense equipment, transportation, medicine and other applications.

In this study, steel is used as the base metal. Corrosion is the result of chemical and electrochemical reactions

that occur spontaneously in the environment [2]. There are different types of corrosion that can be uniform corrosion,

Coatings

In the past few decades, coating technology has become a broad field of research in the field of materials science.

Today, in addition to the protective role of the coating and its decorative application, the industry demands better properties of the coating.

Recent advances in polymer science, especially at the nano level, have greatly contributed to the advancement of this growth, especially in the field of corrosion.

Metal Coatings

Metal coatings can be applied to metallic and non-metallic surfaces. Among the important metal coating methods is electroplating[8].

Electroplating is an electrochemical method with an electrolytic process. In this process, metal ions in an electrolyte solution are deposited on the cathode.

In the electrolytic process, the anode is usually made of a metal that has been plated, thus serving as the source of the coating metal

And the workpiece, where the coating is applied, acts as the cathode. Direct current from an external power source passes through the electrolyte solution.

The electrolyte conducts the electric current by moving the plating metal ions in the solution.

Barrel plating[9], rock plating[10] and strip plating[11] are the most important plating methods.

Different metals are used in plating, the most important of which are zinc, nickel, gold, tin and alloy plating [4].

Inorganic coatings

Inorganic coatings are applied to submicron-sized particles by one of two methods: deposition of inorganic coatings on the particles or the sol-gel process. The advantage of these coatings is that nanoparticles can be coated with minerals to create new properties [5].

Polymer coatings

Polymer coatings have made it possible to control the compatibility of the polymer with the matrix and the strength of the interaction.

The coating is attached to the particle surface, then the coated particles can be easily dispersed in a matrix with similar chemistry to produce composites. The particles can be prepared by living radical polymerization in the form of composites without additional matrix.

Polymer coatings are widely used as protective and decorative coatings in the paint industry [5].

Paints

Resin, pigment, solvent and additives are the main components of paints.

The properties of paints are mostly related to the resin and are classified based on the type of resin or the method of drying the resin.

Classification of paints

Paints are divided into two categories according to their type of hardening: physical drying[12] and chemical drying[13].

The type of hardening affects the amount of coverage and protection of the paint. In physical drying

With the evaporation of the solvent, the resin molecules are connected to form a film. Drying depends on the duration of solvent evaporation and hardening

of the coating. The characteristics of this type of coating include solubility in the main solvent and softening at high temperatures

Corrosion of metals