Enamel Coating Line

Enamel coating line is a featured high temperature application system. Enamel coating requires pretty high temperature to work with(900~950℃）. It’s widely used on elegant home appliance products such as electric water heater and cookwares such as different pots and pans. Being a professional enamel coating line provider, AFNT group has been working closely with multiple enemal manufacturers for leading production line solutions such as coating line design, spare parts supply, maintenance and consulting service etc.

Enamel coating line process

Pre-treatment stage

Degreasing Metal substrates (such as common iron and steel substrates) will be stained with oil stains during processing and storage. Oil removal generally adopts chemical oil removal method, using alkaline degreaser, through heating and stirring, so that the degreaser and oil stain fully react with the oil stain to remove the oil stain from the metal surface. This is like giving the metal matrix a “degreasing bath” to provide a clean surface for subsequent processing.

Electrochemical degreasing can also be used, and direct current is used in alkaline solution to accelerate the emulsification and removal of oil stains, which is more efficient, especially for workpieces with complex shapes.

Rust removal
The surface of the metal matrix may rust due to oxidation, and pickling methods are commonly used to remove rust. The metal matrix is immersed in a certain concentration of acid solution (such as hydrochloric acid, sulfuric acid, etc.), and the acid reacts chemically with the rust to dissolve and remove the rust. However, the pickling time should be strictly controlled, and too long time will corrode the metal matrix itself.

Mechanical rust removal methods such as sandblasting, shot blasting, etc. can also be used. Sandblasting uses compressed air to spray sand particles onto the metal surface to remove rust layer and oxide scale; Shot blasting is to throw the projectile at the metal surface through a high-speed rotating shot blaster to achieve the purpose of rust removal and strengthening of the metal surface.

Neutralization and cleaning
Acid residue will remain on the surface of the metal matrix after pickling, which needs to be neutralized. Lye solution (such as sodium hydroxide solution) is generally used to neutralize the metal surface.

After neutralization, it should be cleaned multiple times, first rinsing with running water, and then cleaning with deionized water or pure water to ensure that there are no residual acids and alkalis and other impurities on the metal surface, providing a good foundation for subsequent enamel coating adhesion.

The primer glaze coating stage

Preparation of primer glaze
The primer glaze is a homogeneous slurry made of a variety of inorganic oxides (such as silica, alumina, boron oxide, etc.) and a small amount of flux, colorant, etc. through batching, grinding, screening and other processes. The ratio and preparation process of these components will directly affect the properties of the base glaze, such as adhesion, corrosion resistance, etc.

Underglaze is applied
The pre-treated metal matrix is immersed in the primer glaze slurry, or the primer glaze is evenly coated on the metal surface by spraying, leaching and other methods. The thickness of the enamel should be strictly controlled, generally between tens and hundreds of microns according to product requirements.

After enameling, let the base glaze dry naturally in the air for a period of time to evaporate the water and form a uniform base glaze layer.

Furnace installation

The metal matrix coated with the primer glaze is carefully loaded into the enamel firing furnace, and the placement should be reasonable to ensure that each workpiece can be heated evenly. At the same time, care should be taken to avoid collisions between workpieces to prevent damage to the base glaze.

Firing
Firing is a key part of enamel coating, which causes physical and chemical changes between the base glaze and the metal matrix through high-temperature heating, forming a strong bond. The firing temperature is generally around 800 – 900 °C, depending on the composition of the base glaze and the material of the metal matrix.

During the firing process, the heating speed, holding time and cooling speed should be strictly controlled. Insufficient heat preservation time will make the base glaze not firmly bonded with the metal, and improper cooling speed will also affect the quality of the enamel layer.

Characteristics of enamel coating

• high temperature resisting coating can spray all kind of Metal powder, such as Ceramic powder ( Chrome oxide, Titanium oxide, Aluminum oxide, aluminum titanium oxide, Zirconium oxide powder, etc.), Alloy powder (WC-Co, Cr3C2-NiCr), Chrome, Titanium, Silicon powder, etc.
• Inert gas can be used as working medium to reduce the oxidation of spraying particles.
• The coating can get high bond strength, low porosity. You can get accurate coating by controlling technological parameter.
• Provide protection against high temperatures, corrosion, erosion, wear-resisting effect,prolong lifetime.
• Change appearance, electrical or tribological properties of the surface, replace worn material
• Sprayed on substrates of various shapes and removed, free-standing parts in the form of plates, tubes, shells, etc.
• Powder processing (spheroidization, homogenization, modification of chemistry, etc.)

Enamel coating line FAQ

How’s different of enamel coating line?

The main difference is about curing oven and the spray technologies. Depends the enamel material you use, there’re multiple solutions to be applied.

How to ensure safety during operation?

The coating line is fully automatic, workers just handle loading/unloading part. Danger of the system is on curing oven for its high temperature, it’s not suggested to touch it directly. We’ll configure a fence or protection cover to ensure sefety.

What kind of service customer receive?

We provide turnkey service for this project. You just tell us the requirement then we’ll design and program everything till the line is working perfect in your factory.

What’s the payment term and general delivery time?

We currently only accept T/T transfer, all payments should be cleared before delivery. Producing in factory takes around 30-60 days after received your deposit.