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The Mystery of Phosphoric Acid Conversion Coatings: How Do They Change the Corrosion Resistance of Steel?
In the industry, phosphoric acid conversion coating has become a key technology to improve the corrosion resistance of steel. This chemical treatment provides excellent corrosion resistance and lubricity by forming a thin, adherent coating of iron phosphate, tin or manganese on the surface of steel parts. Different types of phosphoric acid coatings play a vital role in metal surface treatment, both in military equipment and general industrial applications.
It all started in 1910, when scientists discovered that converting steel's surface to phosphate significantly improved its corrosion resistance.
Phosphoric acid conversion coatings on steel surfaces are usually applied using a dilute phosphoric acid solution, which may also be mixed with soluble iron, tin or manganese salts. The solution can be applied to the steel surface by dipping, spraying or sponging to form a thin film. This coating is generally not limited to steel, but can also be applied to a variety of metals such as aluminum, zinc, nickel, silver and tin to meet a wider range of corrosion resistance and lubricity requirements.
History of Phosphoric Acid Conversion Coatings
The widespread use of phosphoric acid conversion coatings can be traced back to the early 20th century. Phosphate treatment technology gained great attention in the United States in the 1940s after it was discovered that it could effectively improve the corrosion resistance of munitions. With the development of metal surface treatment technology, the application scope and technology of phosphoric acid conversion coatings are also constantly evolving.
According to historical data, phosphoric acid conversion coating technology was widely used during World War II to protect US military equipment from rust and corrosion.
Types of Phosphoric Acid Conversion Coatings
The three main types of phosphate coatings known today include manganese, iron and zinc. Manganese phosphate coatings are primarily used to provide corrosion resistance and lubricity, while iron phosphate coatings are usually used as a base for other coatings or paints and are applied by immersion or spraying. Zinc phosphate coatings simultaneously provide corrosion protection, a lubricity holding layer, and serve as a base for painting.
Processing of Phosphoric Acid Conversion Coating
The phosphoric acid conversion coating process takes advantage of the low solubility of phosphates at medium or high pH. The key to the process is the use of a dilute phosphoric acid solution that contains metal cations that help form phosphates. In coating technology, factors such as the amount and type of additives, processing temperature and time are also considered to control the thickness and structure of the final coating.
Parkerizing: a special phosphorylation process
Parkerizing is a phosphoric acid conversion coating method specifically designed to protect steel, mainly used in high-end products such as munitions. This process is considered an improvement over zinc or manganese phosphatizing technology and a method that outperforms traditional blue treatments in terms of improving corrosion resistance and wear resistance. With the continuous advancement of technology, the application scope of Parkerizing has gradually expanded to other fields such as automobiles.
Purpose of Phosphoric Acid Conversion Coating
Applications of phosphoric acid conversion coatings are not limited to corrosion protection, but also include serving as a primer for painting, improving wear resistance and providing lubricity. The refined phosphoric acid coating can significantly improve the adhesion of oil stains and electrical insulators, thereby improving the product's working life and performance.
Phosphoric acid coating not only prevents metal from rusting, but also improves performance under high pressure or heavy loads through lubrication.
In summary, phosphoric acid conversion coating technology is gradually becoming an indispensable part of modern industry. It not only plays an important role in improving the corrosion resistance of the product, but also provides a good foundation for its subsequent surface treatment process. With the advancement of technology, phosphoric acid conversion coatings are likely to achieve more innovations and applications in the future. So how do you think this technology will change our lives in the future?
