Even that is expensive than Ni coating and Zn coating.People still want to buy. Why?
Because Parylene is a new conformal coating material developed and applied by UnionCarbide Co. in the United States in the mid-1960s. It is a polymer of para-xylene. , D type, F type, HT type and many other types.
Parylene is a protective polymer material, which can be vapor-deposited under vacuum. The good penetrating power of Parylene active molecules can form a transparent insulating coating with no pinholes and uniform thickness inside and around the element, providing the element with a uniform thickness. A complete high-quality protective coating, resistant to acid, alkali, salt spray, mold and various corrosive gas parts. Because Parylene is not a liquid, there will be no meniscus formation and bridging during the coating process.
Why is NdFeB permanent magnet coated with Parylene?
NdFeB permanent magnet material is a kind of high-performance strong magnetic material, but this material is very unstable in the air. Larger sizes usually use electroplating or epoxy electrophoretic paint as protective coating. In particular, toroidal and cylindrical magnetic materials, it is difficult to meet the requirements for use by the above-mentioned traditional methods of protection. The combination of Parylene’s unique preparation process and excellent performance enables it to be applied to small and ultra-small magnetic materials without weak points. The magnetic material can be immersed in hydrochloric acid for more than 10 days without corrosion. Parylene is used as insulation and protective coating.
Preparation of Parylene film
The commonly used method for preparing parylene is chemical vapor deposition (CVD), which is a process in which a reactive substance undergoes a space-phase gas-phase chemical reaction under gaseous conditions, directly generates a solid substance on the surface of a solid substrate, and then forms a coating on the substrate surface technology.
The preparation process of Parylene film is divided into three steps: vaporization of the monomer, cracking, and adhesion deposition on the surface of the substrate.
1. In a vacuum environment, the solid tetrachloro-p-xylene ring dimer rises to a gaseous state at about 150 ° C;
2. At about 650 ° C, the tetrachloro-p-xylylene ring dimer is cleaved into active 2,5-dichloro-p-dimethylenebenzene with free radicals;
3. At room temperature (25 ° C), free 2,5-dichloro-p-dimethylenebenzene is deposited and polymerized on the surface of a solid substrate to form a pinhole-free conformal film.
Protective effect of Parylene coating
1. Resistance to acid and alkali corrosion, can solve the problem of corrosion by acid or alkaline substances.
2. Low water, gas permeability, high barrier effect, can achieve moisture, water, rust and weathering.
3. Resistant to organic solvents (not soluble in general solvents).
4. The film is colorless and highly transparent, and does not affect the original appearance of the product.
5. The membrane layer is dustproof, moisture-proof, waterproof and breathable, which can make the product meet the international dust-proof and waterproof IP rating specifications.