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Chemical coloring of metals is the process of changing the color of metal surfaces with different chemical solutions. The chemical coloring of metals can be split into three types: electroplating – coating the metal surface with another metal using electrolysis. patination – chemically reacting the metal surface to form a colored oxide or ...
Electrochemical coloring of metals is a process in which the surface color of metal is changed by electrochemical techniques, i.e. cathodic or anodic polarization. The first method of electrochemical coloring of metals are certainly Nobili's colored rings, discovered by Leopoldo Nobili , an Italian physicist in 1826.
The chromate coating acts as paint does, protecting the zinc from white corrosion, thus making the part considerably more durable, depending on the chromate layer's thickness. [ 8 ] [ 9 ] [ 10 ] The protective effect of chromate coatings on zinc is indicated by color, progressing from clear/blue to yellow, gold, olive drab and black.
A conversion coating is a chemical or electro-chemical treatment applied to manufactured parts that superficially converts the material into a thin adhering coating of an insoluble compound. These coatings are commonly applied to protect the part against corrosion , to improve the adherence of other coatings, for lubrication , or for aesthetic ...
[5]: 394 It has also been known as pickling in the context of wrought iron and steel. [11] Parkerizing is commonly used on firearms as a more effective alternative to bluing, which is an earlier-developed chemical conversion coating. It is also used extensively on automobiles to protect unfinished metal parts from corrosion.
Chemical conversion coatings are another effective method for surface protection. These coatings are typically formed through chemical reactions between the metal substrate and a chemical solution. The conversion coating chemically reacts with the metal surface, resulting in a thin, tightly adhering protective layer.
In chemistry, chromism is a process that induces a change, often reversible, in the colors of compounds.In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter the electron density of substances.
These electrons change the valency of the metal atoms in the oxide, reducing their charge, as in the following example of tungsten trioxide: [7] WO 3 + n(H + + e −) → H n WO 3. This is a redox reaction since the electroactive metal accepts electrons from the electrodes, forming a half-cell. [7]