๐๐ก๐ง๐๐๐ข๐ฅ๐ฅ๐ข๐ฆ๐๐ข๐ก ๐ง๐๐๐๐ก๐ข๐๐ข๐๐ฌ / ๐ฆ๐ฎ๐ฐ๐ฟ๐ถ๐ณ๐ถ๐ฐ๐ถ๐ฎ๐น ๐ฎ๐ป๐ผ๐ฑ๐ฒ๐ / ๐ญ๐ถ๐ป๐ฐ ๐๐น๐ฎ๐ธ๐ฒ
Rust prevention. Iron is a cheap and strong metal to use as a construction material. It has one basic flaw however, it is very reactive. It will quickly rust, under the right conditions, leaving behind a fine brown powder known as iron oxide (rust).
๐ช๐ฒ ๐ฐ๐ฎ๐ป ๐ฝ๐ฟ๐ฒ๐๐ฒ๐ป๐ ๐ถ๐ฟ๐ผ๐ป ๐ณ๐ฟ๐ผ๐บ ๐ฟ๐๐๐๐ถ๐ป๐ด ๐ฏ๐ ๐บ๐ฎ๐ป๐ ๐ฑ๐ถ๐ณ๐ณ๐ฒ๐ฟ๐ฒ๐ป๐ ๐บ๐ฒ๐๐ต๐ผ๐ฑ๐.
- The most common way is to paint the metal and prevent oxygen from reacting with it. This method is very expensive as coats of paint need to be applied frequently. If the surface coating of paint is scratched rusting will take place immediately. This is not the preferred method of rust prevention for giant ships that often scrape against rocks, sand and barnacles.
- Instead as theoretical basis and practical experience, a #sacrificial #anode is used. A sacrificial anode is a block of metal that is more reactive than iron.
๐ง๐ต๐ฒ ๐บ๐ผ๐ฟ๐ฒ ๐ฟ๐ฒ๐ฎ๐ฐ๐๐ถ๐๐ฒ ๐ฎ ๐บ๐ฒ๐๐ฎ๐น ๐ถ๐ ๐๐ต๐ฒ ๐ฒ๐ฎ๐๐ถ๐ฒ๐ฟ ๐ถ๐ ๐ด๐ถ๐๐ฒ๐ ๐ฎ๐๐ฎ๐ ๐ฒ๐น๐ฒ๐ฐ๐๐ฟ๐ผ๐ป๐.
This reactive block of metal acts as a source of electrons for the iron. When oxygen takes electrons from the iron during the process of rusting iron atoms simply take electrons from the reactive metal....
๐๐น๐ฎ๐ธ๐ฒ ๐๐ถ๐ป๐ฐ-๐ฎ๐น๐๐บ๐ถ๐ป๐ถ๐๐บ ๐ฐ๐ผ๐ฎ๐๐ถ๐ป๐ด๐ ๐ฎ๐ฟ๐ฒ ๐๐๐ฒ๐ฑ ๐ถ๐ป ๐ถ๐ป๐ฑ๐๐๐๐ฟ๐ ๐ณ๐ผ๐ฟ ๐ฑ๐ฒ๐ฐ๐ฎ๐ฑ๐ฒ๐.
They can perform high corrosion resistance according to required accelerated tests, but in the field application the corrosion resistance is reduced due to nonuniform thickness of coating layers. In case the same thickness of coating, the corrosion resistance is affected by composition of coating.
Flake zinc-aluminium coatings are used in automotive, aerospace and building industry around whole word for nearly 40 years with different trade names. They are used in wide range of combination of primer zincaluminium layers and coloured or friction inorganic top layers.
๐๐ฐ๐ฐ๐ผ๐ฟ๐ฑ๐ถ๐ป๐ด ๐๐ผ ๐๐ฆ๐ข ๐ญ๐ฌ๐ฒ๐ด๐ฏ ๐๐ต๐ฒ๐ฟ๐ฒ ๐ฎ๐ฟ๐ฒ ๐ณ๐ผ๐๐ฟ ๐ฏ๐ฎ๐๐ถ๐ฐ ๐๐ถ๐ป๐ฐ ๐ณ๐น๐ฎ๐ธ๐ฒ ๐ฐ๐ผ๐ฎ๐๐ถ๐ป๐ด ๐๐๐๐๐ฒ๐บ๐.
The characteristic for these types of coating is shape of pigments, that should be made up horizontally with the metal surface... ๐๐ ๐๐๐๐ ๐ ๐๐๐๐๐๐๐๐๐๐ ๐๐๐ฆ๐๐๐ ๐๐ ๐ ๐๐๐๐, ๐๐ ๐ โ๐๐ค๐ ๐๐ ๐กโ๐ ๐โ๐๐ก๐.
This arrangement creates longer path for humidity and/or pollution to penetrate through coating layers – excellent barrier protection.
The second protective mechanism is cathodic one, because ignoble zinc, as the less noble metal, in the base coat sacrifices itself, corrodes and protects the substrate steel from deteriorating – electrochemical mechanism. In many cases the top layer given passive protection, too... to be continued.
Simone Sanseverinati
#automotive #aerospace #technology
