Passivation is widely used as an effective protective measure for metals and metal coatings in less severe environments.

 The passivation treatment of galvanized checkered plate is a kind of chemical conversion coating treatment. The actual passivation process depends on the electrochemical reaction process on the metal surface. It includes an anodic dissolution step, in which the metal surface is oxidized, and the accompanying cathodic process reduces certain ions in the passivation solution, producing low-valent ions and metal corrosion products to form a passive film on the surface.

1. Chromic acid passivation

    The conventional passivation treatment is chromate passivation. The metal mixture passivation layer formed by this chromate treatment is mainly composed of trivalent chromium and hexavalent chromium. Among them, trivalent chromium is used as the skeleton, and hexavalent chromium is easily exuded from the passive film as a corrosion inhibitor.

    Over the past decade, there has been a profound understanding of the toxicity of chromate, which is highly toxic and carcinogenic. For example, 1-2 grams of chromic acid, or 6-8 grams of potassium dichromate can cause kidney failure, liver damage, blood disorders and death. Long-term exposure to chromate can cause pimples, blistering, and ulcers. Inhalation of chromate can cause lung cancer. Therefore, the country will focus on the control of heavy metal pollution during the 12th Five-Year Plan period, including chromium.

2. Chromium-free passivation

    The seriousness of heavy metal pollution in my country has attracted great attention from the party and the state. Upholding the concept of environmental protection for the people, the Party Central Committee and the State Council have decided to deploy a series of actions to strengthen the prevention and control of heavy metal pollution: research and propose technical standards, policy measures and management regulations for the prevention and control of heavy metal pollution involving lead, mercury, cadmium, chromium, arsenic, etc. , lead, mercury, chromium, cadmium and other heavy metals "high pollution, high environmental risk" product list, comprehensively investigate and rectify heavy metal polluting enterprises, optimize the industrial structure involving heavy metals, improve the heavy metal pollution prevention and control system, accident emergency system and environmental and health risk assessment System and other three major regulatory systems, laying a solid foundation for the effective control of heavy metal pollution. Recently, the "Twelfth Five-Year Plan for Comprehensive Prevention and Control of Heavy Metal Pollution" was approved by the State Council, becoming the first "Twelfth Five-Year" national plan. Therefore, chromium-free passivation is imperative.