2. Surface pre-treatments: degreasing, pickling

In the industrial sector, metal parts are likely to have a wide variety of surface qualities before undergoing surface treatments. Some surfaces may have been machined and are coated with lubricants (greases, surfactants, etc.). Other surfaces are the result of foundry or wrought operations (rolling, hot forging...) and are covered with a layer of hot-formed oxide.

The aim of the degreasing operation is to remove the "contaminated" surface area containing traces of mineral, vegetable (ester), surfactant or other oils.

Next, the pickling operation removes the oxidized zone created by the previous operations, essentially consisting of hot-formed oxide. $\left({\text{Al}}_2{\text{O}}_3\right)$...