First of all, it must be clear that the passivation phenomenon is caused by the metal phase and the solution phase, or by the interface phenomenon. Nano-ceramic solution Take 2mL ceramic working solution into 250mL conical bottle, add 10mLP1 buffer, shake well, then add 20mLP2 buffer, shake well, and add 2-3 drops of HP indicator. It was heated to 80~90℃ in the electric furnace, and titrated with 1m mol\/L EDTA standard solution quickly while hot. The solution changed from wine red to light yellow as the titration end point. The ML number of standard liquid used was recorded, and the number of ceramic liquid was 5V. At present, most of the ceramics use phosphating process, with the continuous advancement of energy conservation and emission reduction, the new phosphorus free conversion film ( Ceramic film) is quietly replacing the traditional phosphating film. Ceramic liquid should be the so-called zirconium series, zirconium titanium series, silane series, zirconium silane series, and other non-phosphorus metal surface treatment agents, which can partially replace phosphating liquid, the main raw materials are fluorozircoate, silane coupling agent, etc. The effect of mechanical scraping on passivated metals has been studied. The experiment shows that when the metal surface is continuously scraped during the measurement, the electric potential of the metal moves violently in the negative direction, that is, the dressing of the metal surface can cause the activation of the metal in the passive state. It is proved that the passivation phenomenon is an interfacial phenomenon.
What is the passivation mechanism of aluminum alloy? It changes at the interface between metal and medium under certain conditions. Electrochemical passivation is when the anode is polarized, the potential of the metal changes and metal oxides or salts are formed on the electrode surface. These substances are closely covered on the surface of the metal as a passivation film, resulting in metal passivation. Chemical passivation is the direct action of concentrated HNO3 and other oxidants on the metal to form an oxide film on the surface, or the addition of easily passivated metals such as C
Caused by R, Ni, etc. Nano-ceramic solution Take 2mL ceramic working solution into 250mL conical bottle, add 10mLP1 buffer, shake well, then add 20mLP2 buffer, shake well, and add 2-3 drops of HP indicator. Heated in the electric furnace to 80~90℃, titrated with 1m mol\/L EDTA standard solution quickly while hot, the solution changed from wine red to light yellow as the titration end point, recorded the standard liquid millilitre V, ceramic liquid The number of points is 5V. When chemical passivation, the concentration of the oxidizer added should not be less than a certain critical value, otherwise it will not lead to passivity, but will cause faster dissolution of the metal.
Due to the active chemical properties of aluminum, aluminum and aluminum alloy products are often oxidized in the process of air contact, and a dense alumina layer is generated on the surface to protect the internal structure of aluminum and aluminum alloy products. However, in some special environments, such as contact with strong acids or alkali, the alumina layer will further react with hydrogen ions or hydroxide ions, and cannot protect the internal structure of aluminum and aluminum alloy products, so aluminum and aluminum alloy products are often passivated in industrial production to meet the needs of special environmental use.
The traditional technology is achieved by removing the oxide layer on the surface of aluminum and aluminum alloy products and then soaking aluminum and aluminum alloy products in passivation solution to form a passivation layer.
For the purpose of aluminum and aluminum alloy products, chromium compounds are often used as passivation fluids in passivation operations to ensure the corrosion resistance of aluminum and aluminum alloy products. However, since chromium trivalent and chromium hexavalent are heavy metals with strong carcinogenicity, they are easy to be enriched in the human body during the production process, causing damage to human health, and the heavy metals will cause irreversible damage to the environment after being discharged with the production waste liquid.