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From chromate passivation to chromium-free passivation, what kind of advancement has the galvanized passivation technology experienced?

From chromate passivation to chromium-free passivation, what kind of advancement has the galvanized passivation technology experienced?

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  • Time of issue:2023-03-16
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(Summary description)As a surface-covering protective layer, metals often require additional protective measures to ensure that they meet the corrosion resistance requirements in a certain environment. For example, when zinc is used as a metal surface covering layer, it needs to have sufficient thickness to protect the base metal, mainly relying on the sacrificial anode function of the zinc layer and the dense basic zinc carbonate film formed on the zinc surface in the atmosphere and neutral water environment isolation protection.

From chromate passivation to chromium-free passivation, what kind of advancement has the galvanized passivation technology experienced?

(Summary description)As a surface-covering protective layer, metals often require additional protective measures to ensure that they meet the corrosion resistance requirements in a certain environment. For example, when zinc is used as a metal surface covering layer, it needs to have sufficient thickness to protect the base metal, mainly relying on the sacrificial anode function of the zinc layer and the dense basic zinc carbonate film formed on the zinc surface in the atmosphere and neutral water environment isolation protection.

  • Categories:News
  • Author:
  • Origin:
  • Time of issue:2023-03-16
  • Views:0
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As a surface-covering protective layer, metals often require additional protective measures to ensure that they meet the corrosion resistance requirements in a certain environment. For example, when zinc is used as a metal surface covering layer, it needs to have sufficient thickness to protect the base metal, mainly relying on the sacrificial anode function of the zinc layer and the dense basic zinc carbonate film formed on the zinc surface in the atmosphere and neutral water environment isolation protection.

However, in a humid and unventilated environment, the zinc layer corrodes quickly, and the white loose product formed cannot protect the zinc layer from further corrosion, that is, white rust occurs. Common additional anti-corrosion measures include phosphating and chromate passivation. Among them, passivation is widely used as an effective protective measure for metals and metal coatings in less harsh environments.

Passivation treatment is one of the chemical conversion film treatment processes, the principle of which is to change the metal surface from an activated state to a passivated state, thereby slowing down the dissolution of the metal. 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 some ions in the passivation solution, and the generated low-valent ions form a passivation film on the surface together with the corrosion products of the metal .

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, of which trivalent chromium is used as the skeleton, and hexavalent chromium (chromate ion) is easy to seep out of the passivation film as a corrosion inhibitor.

Chromate passivation is widely used in aviation, electronics and other industrial sectors because of its low cost, simple use, and can improve the corrosion resistance of metals. Since it was first applied to magnesium in 1924, chromate passivation has been widely used in aluminum, zinc, tin, cadmium, copper, silver and many other metals and their alloys. The chromate passivation treatment methods include direct immersion method and electrochemical treatment method, etc., and the solutions used all contain chromium in hexavalent form.

In the past ten years, people have gained a deep understanding of the toxicity of chromate, which is considered to be highly toxic and carcinogenic. For example, 1-2g of chromic acid or 6-8 potassium dichromate can cause kidney failure, liver damage, blood disorder and death; long-term exposure to chromate can cause papules, bubbles, and ulcers; inhalation of chromate can cause liver cancer.

Therefore, the level of chromate in the workplace is strictly regulated by the government, and those who use chromate must be informed of the possible health risks of chromate. OSHA (Occupational Safety and Health Association) of the United States stipulates that the content of insoluble chromate in the air should be less than 1mg/m3 in the workplace of 40 hours a week and 8 hours a day.

With the strengthening of people's awareness of environmental protection, chromate is so harmful to people's health that it inevitably leads the government to strictly limit the use and discharge of chromate. To solve this problem, there are basically two ways. One way is to use safer production processes, including the use of protective clothing, gas masks, processes that reduce hexavalent chromium to trivalent chromium, and the use of chromium-free passivation processes. In the future, restrictions on chromate may be more stringent, and this approach does not ultimately address the issue of chromate emissions.

Another approach is to look for low or non-toxic chromate alternatives. Among the main research systems for replacing hexavalent chromium passivation at home and abroad, the organic-inorganic composite technology based on silane materials is an advanced technology respected internationally, and it is also a research hotspot in the world.

Qingdao Haiyida New Material Technology Co., Ltd. is a high-tech enterprise focusing on the research and development and application of new water-based metal surface treatment technology. New technologies and new materials such as environmentally friendly alternatives.

Silane metal surface treatment agent is a new type of organosilicon composite metal surface treatment agent independently developed, which forms an intermediary layer connecting organic and inorganic combinations through silicification reaction on the metal surface, so as to replace the hexavalent chromium passivation purpose of the craft. Compared with the traditional hexavalent chromium passivation treatment agent, the silane metal surface treatment agent does not contain heavy metal ions such as Cr6+ (the product has passed ROHS testing), and does not contain chromate, nitrite, phosphate, F-, etc. The material does not need to be heated during use, and does not need to be washed after treatment. The process flow is simpler. In theory, there is no need to change the tank.

In the future, with the continuous acceleration of the environmental protection process of industrial production, the chromium-free passivation technology with excellent performance and green environmental protection will become the mainstream trend in the field of galvanized passivation.

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From chromate passivation to chromium-free passivation, what kind of advancement has the galvanized passivation technology experienced?

As a surface-covering protective layer, metals often require additional protective measures to ensure that they meet the corrosion resistance requirements in a certain environment. For example, when zinc is used as a metal surface covering layer, it needs to have sufficient thickness to protect the base metal, mainly relying on the sacrificial anode function of the zinc layer and the dense basic zinc carbonate film formed on the zinc surface in the atmosphere and neutral water environment isolation protection.
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