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Rust prevention refers to the surface protection treatment to prevent iron components or equipment from forming iron oxide. The main methods include thermal spraying, hot dipping, coating, soaking or spraying corrosion inhibitor, antirust oil and antirust paint, using passivation solution, electroplating, baking enamel, surface transformation improvement technology, and surface diffusion infiltration technology.

The article must be pretreated with surface cleaning and drying before the anti-rust process. The most appropriate method should be selected according to the properties of the article and the processing conditions. There are three commonly used treatments: solvent cleaning, chemical cleaning, and mechanical cleaning. After cleaning, it can be dried with filtered compressed air or dryer, or wiped with clean gauze.

Metal rust is mainly affected by the following factors:
·  Chemical composition and structure of the metal material.
·  Metal surface finish.
·  Composition and pH value of the solution in contact with the metal surface.
· Temperature and humidity.
·  Environmental media in contact with the metal surface.

There is an easily overlooked factor in the use of outdoor furniture, that is hand sweat. Sweat is a colorless, transparent, or sometimes light-yellow liquid that has a salty taste and weak acid. Its pH value is 5 – 6. In addition to sodium, potassium, calcium, magnesium, and salt, it also contains a small number of organic acids such as urea, lactic acid, and citric acid. When sweat comes into contact with metal, it will form a film on the surface, which will cause electrochemical action on the metal and bring corrosions.

The deterioration of metals caused by the environment and medium is very common. The destruction of most metal articles is related to corrosion factors except for a few precious metals such as Au and Pt. Metal corrosion causes huge losses to society, therefore, anti-corrosion has become a critical issue that must pay attention to.

Anti-corrosion

Corrosion is one of the major causes of damage to metal products, specialized anti-corrosion solutions should be applied to prolong the life cycle of metal products according to the feature that metal products are easily corroded. Chemical, physical, and electrochemical protection are the most common methods.

Corrosion can be categorized into five types, general corrosion, pitting, intergranular corrosion, selective corrosion, and stress corrosion cracking. General corrosion affects the entire surface of a metal, commonly known as rust. Pitting occurs in the small holes on the surface of the material, and these holes become larger over time. Intergranular corrosion is almost invisible on the surface as it takes place inside. Selective corrosion erodes only components of complex materials. This type of corrosion starts from the surface and then penetrates to the interior and corrodes at different speeds. Stress corrosion cracking happens when the material bears the ultimate tensile strength.

Four Common Anti-Corrosion Methods:

Structural Reforming

Some heavy metals are low chemical active and not easily corroded, so the service life of the compound metal is extended with a great margin when adding heavy metals to other metals. People mix nickel, chromium, etc. with steel to make stainless steel, for instance.

Protective Layer

There are two types of protective layers metal and non-metal. Common non-metal layers include oil paint, ceramic, and plastic coatings. Electroplating and hot plating generally use non-corrosive metals, such as zinc, tin, chromium, or nickel to form an oxide film on the surface.

Electrochemical Protection

Electrochemical protection is a method based on the galvanic cell theory by eliminating the galvanic cell reaction which is the cause of chemical corrosion. The cathodic method is more widely used than the anodic method.

Corrosive Medium Treatment

This method is achieved by eliminating corrosive medium. In other words, keeping the metal machinery dry, to name a couple, wiping off the moisture on the equipment, or adding a corrosion inhibitor to corrosive medium.

Powder-coating is to coat powdered paint on the workpiece with an electrostatic spray molding machine. The powder will be evenly attached to the surface in the electrostatic field. Final layers vary in effects according to different paint. The thickness reaches up to 60 microns after high-temperature drying, leveling, and curing, which makes the product surface flat and smooth with strong acid resistance, alkali resistance, and wear resistance, and can withstand long term UV radiation and acid rain without coating pulverization, fading, and falling off.

Powder coating is better than paint spraying in terms of mechanical strength, adhesion, corrosion resistance, aging resistance. The cost is also lower for the same effect. Powder-coating characteristics

  • The final film is flat and smooth with very strong adhesion and excellent decoration performance, under the influence of electrostatic effect.
  • Electrostatic adsorption reduces paint mist pollution and improves the workshop’s hygiene condition.
  • Reduces cost by increasing paint utilization.

Powdered paint

The paint is produced by processing hot extrusion, grinding, and sieving with a mix of specialized resin, pigment, fillers, curing agents, and other additives in certain proportions. It is a solid fine powder that is completely different from coatings in general, very stable at room temperature.

Electroplating refers to the technology of coating a layer of other metals on the surface of the conductors by applying the principle of electrolysis, to prevent metal oxidation such as rust, improve wear resistance, conductivity, reflection, corrosion resistance, and enhance appearance. In addition to conductors, electroplating can also be used on plastics with special treatment.

The electroplated layers are more evenly distributed than the hot-dipped layers. Generally, it’s very thin, ranging from several to tens of microns. Through electroplating, decorative, protective, and functional layers can be obtained on mechanical products. The worn-out and failed workpieces can also be repaired.

Electroplating is not only an electrochemical process but also a redox process. Immerse the components in the metal salt solution as the cathode, and the metal plate as the anode, the required coating will deposit on the components when connecting to the power supply. According to the coatings, it can be categorized into chroming, coppering, cadmium plating, tinning, and galvanizing. It can be divided into a protective coating, protective and decorative coating, decorative coating, corrective coating, and functional coating, based on the applications.

Mainly related to the size and batch of parts to be plated, electroplating includes rack plating, barrel plating, continuous plating, and brush plating, Rack plating is suitable for general-sized products, such as car bumpers, bike handles, etc. Barrel plating applies to small parts, fasteners, washers, and pins, etc. Continuous plating is used for the mass production of wires and strips. Brush plating is for partial plating and repair.

Galvanizing

Galvanizing is a process of forming an evenly distributed, dense, and well-bonded metal or alloy deposition layer on the surface of the workpieces by electrolysis. Compared with other metals, zinc is relatively easy to be plated. It is a cost-effective anti-corrosion electrodeposited coating that allows Canaan Site Furnishings being able to always provide great value products with competitive prices. The galvanized steel frames and components prevent products from corrosion and ensure product service life.

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