Molecular H2CrO4 has a lot in common with H2SO4

British scientists have developed a safer and more functional chromium plating, which is commonly used on old-fashioned car bumpers, steel camshafts, door furniture, lighting and other fixed devices.

Chromium plating can prevent corrosion and increase pleasant luster, but chromium poses serious health risks, and chromium compounds have been proven to cause cancer.

At a meeting at the Chester Institute of physics in the UK, Professor Robert akid warned that workers were being exposed to chromium compounds that could cause cancer and urgently needed a safer alternative. He said at the meeting that the new application of surface modification is organized by the applied physics and Technology Department of the Institute of physics. He and his colleagues are developing an alternative that is not only safer, but also cheaper by reducing a large number of processing stages related to traditional electroplating.

Professor akid is the director of the Research Center for structural materials and integrity of Sheffield Harlem University. He is developing a so-called "sol-gel technology", that is, adding colloids of nanoparticles into the solvent can form a gel. When a metal object is sprayed or immersed in a sol-gel system, it will quickly form a gel like layer on the surface of the object. The solvent is then removed by evaporation and the coating is cured or hardened. Akid said that the sol-gel method can be used to cover a wider range of metals than the electroplating method.

Professor akid said: "these inorganic organic mixed coatings have the potential to become an effective method for producing low-cost corrosion-resistant or functional coatings. This technology can be formulated and cured to provide high corrosion-resistant ceramic based coatings. This method uses different curing temperatures, and the coatings can be cured quickly. The chemical properties of the formula have also been developed to provide sol-gel solutions with good shelf life."

However, the Sheffield team still needs to solve some technical problems. For example, a prerequisite for anticorrosive coatings on metals, such as aluminum and other metal surfaces, including zinc, stainless steel and magnesium, is that they should be thick enough to provide sufficient life and hardness to prevent scratches and wear.

Up to now, the sol-gel derived layer can only be formed to a thickness of 200-300 nanometers by one-time immersion plating. Akid explained that it is possible to produce multiple coatings by double dip method, but this has a potential disadvantage, that is, the reduction of coating performance.

Akid said: "this new protective coating not only has high corrosion resistance, but also is not easy to release its components into the environment, and is non-toxic." Akid and his colleagues used a sol-gel mixture to produce aluminum oxide and silicon oxide coatings, whose chemical composition allows them to adhere to the surface of metal components.

The team's preliminary corrosion tests, including so-called dynamic potential polarization, in which current induced corrosion is used, show that the coating has excellent corrosion resistance compared with uncoated samples and other pretreatment. The researchers also carried out mechanical tests, and through simple scratch and bending tests, it was shown that this coating has very good adhesion to the substrate.

As a further test of the durability of the coating, the researchers also immersed the coating components in a exfoliating solution composed of nitric acid and chloride, with a very high acidity, Ph1. This simulates the corrosion that aluminum alloy aviation components may experience, although it is an accelerated test. Akid explained that their test results were very good compared with similar tests of bare and H2CrO4 anodized samples. The sol-gel composite coating was hardly corroded after immersion for 200 hours. After this, the chromic acid anodized components were pitted, so the test failed, and the bare simple components were severely corroded. The research team used scanning electron microscopy (SEM) to determine the nature of the attack, general or local corrosion.

Molecular H2CrO4 has a lot in common with sulfuric acid (H2SO4). Only sulfuric acid can be listed as part of 7 strong acids. Due to the laws related to the concept of "first-order ionization energy", the first proton is most likely to be lost. Its behavior is very similar to that of sulfuric acid deprotonation. Since there is more than one proton in the process of multivalent acid-base titration (especially when the acid is the starting material and the base is the titrant), the proton can only leave one acid at a time.

Article source: https://article-realm.com/article/Finance/27657-Molecular-H2CrO4-has-a-lot-in-common-with-H2SO4.html