Metal surface passivating treatment fluid

Abstract

The invention discloses a metal surface passivating treatment fluid which is characterized by comprising the following components in percentage by mass: 80-120g / l of magnesium fluoride, 5-7g / l of sodium tripolyphosphate, 20-30g / l of sodium fluosilicate, 40-50g / l of hydrochloric acid, 30-40g / l of nitric acid, 80-120g / l of phosphoric acid, 3-4g / l of sulfuric acid, 16-22g / l of calcium nitrate and the balance of water. The metal surface passivating treatment fluid disclosed by the invention is simple and practical in formula and safe, environment-friendly and pollution-free by containing no chromate, forms an oxygen or oxygen-containing particle absorption layer when reacted with a metal surface and achieves the passivation by enhancing the activation energy of electrode reaction and reducing the reaction capacity of the metal surface by changing the interface structure of metal and a solution due to the absorption of oxygen on the metal surface.

Description

technical field [0001] The invention relates to the field of metal surface treatment, in particular to a metal surface passivation treatment liquid. Background technique [0002] An active metal or alloy in which the chemical activity is greatly reduced and becomes a noble metal state is called passivation. If the corrosion product generated by the metal due to the action of the medium has a dense structure, a thin film (often invisible) is formed and tightly covered on the surface of the metal, which changes the surface state of the metal and greatly increases the electrode potential of the metal. The positive direction jumps and becomes a passive state of corrosion resistance. For example, when Fe→Fe++, the standard potential is -0.44V, and it jumps to +0.5-1V after passivation, which shows the performance of corrosion-resistant noble metals. This layer of film is called passivation film. The chemical conversion coating process on the surface of aluminum alloy can be rou...

AI Technical Summary

Problems solved by technology

The chemical conversion coating process on the surface of aluminum alloy can be roughly divided into two types: one is chromate passivation treatment, and the other is non-chromate passivation treatment. Although chromate passivation treatment has many advantages However, due to the high toxicity of (Cr), carcinogenicity, and great environmental pollution, many countries have strictly restricted the use and discharge of chromate, and with the entry into force of EU directives, the use of chromate in metal surface treatment has been extremely restricted. big limit