中文版Screw galvanization
Because the zinc compares with other galvanization with the metal, the price is most inexpensive, and corrosion resistance of the zinc surpasses the steel and iron far in the most situations, the galvanization level can protect in not the continual part, the eyelet, the breakage and the cutting edge place reveals the steel and iron. Therefore the common screw or easy to suffer the atmospheric corrosion function the screw to galvanize mostly, but the screw not image plate either stick such shape does not have the change or the surface is smooth, therefore galvanization level thickness in various spots rare even, often becomes the forehead to be thickest, front end the thread mountain next, the groove of thread is thinnest. In order to coordinate the screw the mass productions, reduces the cost and raises the output, usually uses the galvanizing process to become the barrel galvanization the way, this law is causes the electric current from the bucket rack electrode to pass over in barrel's wire, but wire and screw contact but the electric conduction, simultaneously the barrel rotation stirs the screw, causes the screw and the electrode uniform contact. However this time electric current is off and on, very difficult to form the even current density, therefore galvanization thickness also easy different.
The galvanization galvanization may use the acidic plating solution and the alkalinity plating solution two kinds, the acidic plating solution take the zinc sulfate as the essential component, moderately-priced, and the efficiency is big, the galvanization speed is quick, easy to manage, is also not easier than the alkalinity plating solution the hydrogen embrittlement, but crystallizes slightly thickly, gloss bad, plates ability to be bad. But the alkalinity plating solution take the zinc cyanide as the essential component, although the price is high, but plates ability to be good, so long as manages appropriately, then has gloss coating, if further executes the chromate treatment, then obtains a more luminous coating, and the corrosion resistance is fine.
The galvanizing by dipping also uses in surface of corrosion prevention the screw, the bolt and the cap nut, the galvanizing by dipping screw has the good resistance to corrosion compared to the electricity galvanization screw, the cost is only high, and of the high strength structure is not suitable the galvanizing by dipping with the bolt, because the coating surface easy to form hardly crisp, when high temperature or high load situation possibly has the break.
The galvanization level the durability becomes the linear relationship in the corrosive environment with its thickness, namely a coating thicker life is longer, but in contains industrial district of its corrosion prevention sulfide to be bad, simultaneously will produce in oceanity and the tropical climate massively from the color corrosive product, must serve with the chromate treatment to prevent it. In the US once take membrane thick 0.03mm the thin galvanization preview implementation experiment, the result discovery in the countryside area, the Binhai area and the industrial district the mean lifetime approximately as 3:2:1, expressed that air in the pollution, the galvanization level is easiest to have the corrosion phenomenon, because in the industrial district in the waste gas which will discharge by the factory includes many sulfur oxide compound (SOx) and nitrogen oxide (NOx) will destroy the galvanization level. In the Binhai area, because in the atmosphere the existence will have the massive salty crystallization and the liquid particle (chloride) will create the metal corrosion, and size of also obvious influence corrosion rate atmospheric relative humidity. The Beijing University of Science and Technology Material Protection Research institute also once performed atmosphere of exposition corrosion test the galvanization level in the mainland different area, trial period one year, what the result discovery corrosion rate is highest is in the atmosphere SO2, the chloride (sea salt granule) the content is highest, and relative humidity biggest area. And the atmospheric relative humidity was considered that is creates the corrosion the primary factor, but in the atmosphere the pollutant, specially SO2 and the chloride are the primary factors which the promotion corrodes.
The galvanized screw in the production, the storage, ship in the process, its galvanization level possibly occurs pan-white, changes dark, becomes dark and so on phenomena, is mainly in the galvanization level and the corrosive medium and the atmosphere the moisture, the oxygen, the carbon dioxide contact has the corrosion result. Must prevent this kind of phenomenon, may select the surface condition good material as far as possible before the screw processing, because in the process of galvanization, the screw surface's flaw easy to cause corrosive medium permeating and so on among them acid, alkali, salt, cleans with difficulty causes the corrosion. Processes in the screw when must reduce the stress concentration as far as possible, because of the stress concentration region, has the corrosion very easily in the acid pickling stain removal process. When screw heat treatment must reduce the oxidized film thickness as far as possible, before especially galvanizes, must thoroughly except the superficial greasy dirt and the corrosion and the suitable control acid pickling stain removal time, in order to avoid the influence galvanization quality. Operation of the galvanization needs to pay attention selects good plates galvanization of solution deeply ability, strengthens the tank liquor maintenance management, properly controlling current density and chemical additive amount used. After the galvanization, when must clean thoroughly, eliminates the plating solution and the organic matter to coating the harm, moreover must reduce screw's in atmosphere detection time as far as possible, carries on as soon as possible seals processing. Must choose the packing material reasonably, avoids using and the zinc not accommodating revertex product, the packing is best by the metallic material like galvanized iron sheet, in the packing case may put in the right amount drying agent to reduce in the box the humidity, the storehouse relative humidity must reduce and prevent the noxious gas corrosion.
At present in the market condition one kind of named LONGZINC (the Ducker rust) the metal surface treatment, is suitable for the screw and the cap nut. Its processing mode was soaks already the degreasing and the stain removal screw cap nut plates forms in the Ducker rust rust-preventing agent trough or the use metallizing way in the metal surface protective film of the zinc and the price chromium compound, and dried, after the cooling, was again redundant processes one time, obtained membrane thick approximately 5~8 Mu (, assumed the silver-gray color, provided the material based on the manufacturer to demonstrate that had the good rust prevention, the anticorrosion characteristic. Formosa Plastics Group Mai Liaochang is called this dries duplicate zinc chromates epithelium processing, once experimented, experiments two years later the effect on the high-tensile steel construction bolt is good.
Taiwan galvanization company also once cooperated with the Gongyanyuan material develops one kind of use to resist corrosion high in the screw zinc base alloy coating (aluminum zinc), installs after Taiwan Telegraphic Transmission Corporation telephone pole in on the Penghu outlying islets carries on the anticorrosion experiment, has obtained successfully. Joins the aluminum in the zinc to be possible to enhance coating the anti-corrosive performance, when the aluminum content is 30%, aluminum zinc's corrosion resistance is best, therefore of chemical stability and the corrosion resistance this kind of coating compare galvanize alone are friends with.
