Passivation is the method of converting the metal surface into a state that is not easily oxidized and delaying the corrosion rate of the metal. In addition, an active metal or alloy, which greatly reduced the chemical activity, and become a noble metal state of the phenomenon, also known as passivation.

Phenomenon: metal due to the role of the media generated by the corrosion of the product if it has a dense structure, forming a layer of film (often invisible), tightly covered in the metal surface, the metal surface changes the state, so that the metal electrode potential Greatly to the positive direction of the transition, and become a passive state of corrosion. Such as Fe → Fe + + standard potential of -0.44V, passivation after the transition to +0.5 ~ 1V, and shows the corrosion resistance of precious metals, this film is called passive film.

The passivation of the metal may also be a spontaneous process (such as the formation of a layer of insoluble compound, the oxide film, on the surface of the metal). In the industry is the passivation agent (mainly oxidant) on the metal passivation treatment to form a protective film. Common examples: cold H2SO4 and iron will be passivated.

The Principle of  Passivation

The mechanism of its passivation can be explained by the theory of the film, that is, passivation is due to the role of metal and oxidation, the role of the metal surface to produce a very thin, dense, good coverage, firmly adsorbed on the metal surface Of the passivation film. This layer of film is present as an independent phase, usually a compound that oxidizes the metal. It plays the metal and corrosive media completely separated from the role of metal and corrosive media to prevent contact, so that the metal stopped basically dissolved to form a passive state to achieve the role of anti-corrosion.

Differences between Passivation Treatment and Antirust Oil

Passivation and anti-rust oil is the main difference between the production of different products; anti-rust oil is the use of oil film sealing metal surface pores to achieve isolation and oxygen contact and effectively prevent the role of rust, is a veritable physical response. Oil film is easier to carry out with the production of the removal, destruction of failure; and passivation is the use of passivation fluid in the oxidizing substances and metal redox reaction, to promote the metal surface to generate a layer of metal oxide compounds, to achieve The purpose of metal protection. This process is a chemical reaction. The resulting passivation film is dense and intact is not easily damaged.

The Advantage of Choose Passivation

(1) Compared with the traditional physical closure method, the passivation treatment has the characteristics of increasing the workpiece thickness and changing the color, improving the precision and the added value of the product, making the operation more convenient; (2) because the passivation process belongs to No reaction state, the passivation agent can be repeatedly added to use, so longer life, more cost-effective. (3) passivation to promote the metal surface of the formation of oxygen molecules passive film, film dense, stable performance, and in the air at the same time with self-repair effect, so with the traditional method of anti-rust oil, passivation Of the passivation film is more stable, more corrosion resistance.

The Element of Choose Passivation

(1) Confirmation Material Since stainless steel contains more types, it should be carefully confirmed first. All 300 and 200 series materials can be used ID3000, 400 series recommended ID4000 or ID4001. In the case of

(2) to understand the appearance of passivation of the workpiece to pass the surface effect of the current pass there are two general ways: First, the color that does not change the original color ID3000 and ID4000 belong to this type, the other is silver Wash the passivation effect, more applicable ID4008 We know that iron, aluminum in dilute HNO3 or dilute H2SO4 can quickly dissolve, but in concentrated HNO3 or concentrated H2SO4 dissolved phenomenon is almost completely stopped, carbon steel is usually very easy to rust, if In the steel by adding the right amount of Ni, Cr, it becomes stainless steel.