The Theory Of Dyeing By Dyestuffs

　　There are organic dyeing and inoragenic dyeing,which are two different dyeing methods.

１.The Theory Of Dyeing By Organic Dyes

　　According to adsorption theory of substance,which can be divided into physics adsorption and chemistry adsorption,they have respective charactor.

（１）Physics Adsorption

　　Molecules or ions can be adsorpted by electrostatic force,which is called physics adsorption.The composition of oxide film is amorphous alumina,inner close to aluminum matrix is dense barrier layer whose top produces a trumpet-like patulous multihole construction and can present excellent physics adsorption property.When dye molecules come into the film hole,they will be absorbpted on the wall of hole.

（２）Chemistry Adsorption

　　Molecule or ion can be adsorpted by chemical force,which is called chemistry adsorption.At this point, organic dye molecule store in film hole because of reacting with alumina.There are some way about the chemical combination,for example,oxide film forms covalent bond with the sulpho of dye molecule,oxide film forms hydrogen bond with the phenolic group of dye molecule,oxide film forms complex compound with the dye molecule,etc.Because it’s different from porperty and construction of dye molecule,the productive chemistry adsorption ways are discrepant.

（３）Temperature Requirement

　　Physics adsorption and chemistry adsorption have distinguishing temperature requirement.Physics adsorption needs low temperature,because it is easy to desorb at high temperature.On the contrary,only at certain temperature chemistry adsorption can be done.Chemistry adsorption is greater than physics adsorption.In general,the physics adsorption and chemistry adsorption are performed simultaneously when dyeing,but chemistry adsorption occupies main position,so oraganic dyeing usually should be doing at middle temperature.

２.The Theory Of Dyeing By Inorganic Dyes

　　Inoragnic dyeing is usually doing at room temperature.When dyeing,oxidative work-pieces are firstly dipped in a solution of inorganic salt based on the order,and then dipped on another solution of inorganic salt.The process makes these inorganic substance trigger chemical reaction in the film hole to produce water-insoluble colored compound,fill up the interspace of oxide film and seal up film hole,in some case the sealing treatment of dyeing layer can be canceled and the film layer can present color.

　　The patent of inorganic dyes was published in 1930.At that time, the shop facade and railings, etc. had been using extruding aluminum,the anodizing film was dipped in 20-50g/l of cobalt acetate solution,and then dipped into the potassium permanganate of similar concentration.The two solutions which are at 50℃can dye bronze for oxide film.If the operation is repeated for 2 to 3 times and the deeper bronze can be obtained.Actually,the color range obtained by inorganic dyes is limited and the color is not enough bright but excellent in fastness to temperature and light.Organic dyes will change their color when more than 100℃,while so much equipment of inorganic dye film do not change the color even be heated to the melting point of metal,therefore there are some unique usages at present.

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