中文版Chemistry surface treatment
The metal alloy may in receive situation in the control in the suitable chemistry solution to form the protection surface jacket, namely protective film or chemical conversion membrane. Because it when chemical treatment, of metallic transition the surface forms a body for the compound and the base metal, therefore produces surface layer of the resistance, in physics and the chemical property is a base metal part. The protective film mainly uses in: “the improvement metal surface oxide film's stability, prevents the metal or the coating metal further corrodes in the atmosphere. 2. causes the corrosion of metal to reduce to the lowest degree. 3. enhances the paint, the coating to stick shrinks the nature. Common chemistry surface treatment for parkerising, chromate treatment and oxidized and so on three kinds.
(1) parkerising
The parkerising is puts in the metal includes in the phosphate solution to carry on the chemical treatment, causes the metal surface to form one kind difficult to dissolve in the water and the adhesiveness good phosphate protective film is the phosphate epithelium, the main application to take first floor and the metal cold finishing time the paint lubricant adsorbed layer. Because the phosphate epithelium is by a series of size different zinc, the manganese, the hard hydrophosphate and the phosphate crystal is composed, therefore the film is porous, the surface area is big, has the very good adsorbability, can adsorb the paint vehicle or the massive lubricants, therefore often serves as the paint the first floor, or cold stamping reduction friction and steel pipe, steel wire hard-drawn lubricant film. The phosphate epithelium does not dissolve in the water, is very stable under the atmosphere, can take the rust prevention request not high protector, if carries on again the phosphate epithelium chromic acid saline membrane sealed processing, the gumming or the coating, may further enhance its resistance to corrosion.
The phosphate epithelium becomes of shielding systems the resin varnish composition with the nitrolac or Taiwan to have the very good corrosion prevention function to the steel and iron, when modulation paint vehicle should enable its viscosity to cause the paint vehicle free penetration iris opening, the varnish film dry temperature suitably at 150~180℃, should better dry in the drying oven. When the phosphate epithelium uses in the cold-work processes and reduces the friction surface abrasion, the film soaks by the oil class or the soap class lubes may enhance its use effect, the simplest effective method is carries on the dipping treatment in the potassium soap solution. What the phosphate epithelium applies is broadest is the iron phosphate membrane, the zinc phosphate membrane and the manganous phosphate membrane, the zinc phosphate membrane and the manganous phosphate membrane the atmosphere in the oxygen oxidation, the corrosion resistance are not been good.
At present Taiwan screw uses raw material mainly by the steel supply, wire rod of the steel production (e.g. major and medium or strong new) processes after the iron and steel plant is made the wire rod, is in luck again to the screw factory. If the material quality for the carbon steel, the processing process forms including the hydrochloric acid acid pickling stain removal and the parkerising has phosphate of epithelium the lubrication, in order to help draws, and the easy cold forging (to push makes hammers thickly). If material quality for alloy steel, after the acid pickling, must the sheroidizing, the annealing forms the mild steel to cause the easy machine-finishing, after again the acid pickling, the parkerising or the lime soap throw over duplicate, pulls out the system. If material quality for stainless steel, then needs the oxalic acid to throw over complex becomes the lubricant film in order to help to pull out the system. After the screw factory completes line of diameter, the real roundness, the superficial scar or the corrosion examination of the wire rod, soon the wire rod directly sends in the shaper to take anticipates the cold forging, passes through again rolls the tooth mechanism to become the screw.
(2) chromate treatment
The chromate treatment is plunges the metal either the metal clad including certain chemical additive chromic acid or in the chromic acid salt brine, uses chemistry or the electrochemistry method, causes the metal surface to form the chromates epithelium's process which is composed of three price chromium and six price chromium. Often serves as the galvanization level (electricity galvanization, galvanizing by dipping, zinc base alloy) and the cadmium plating post-processing, enhances coating the corrosion resistance, may also serve as other metal like aluminum, copper, the tin, the magnesium, the nickel and the alloy superficial corrosion prevention. The chromates epithelium's structure is quite close, adheres the nature to be good, has the good chemical stability, after his/her epithelium dry, for the imporosity, can treat as the impediment to prevent the moisture to arrive at the base metal, has the reliable isolation protective function in the corrosion environment to the metal surface.
The chromates epithelium's essential component is includes three price chromium and six price chromium compound, as well as parent metal or coating metal chromates. And the insoluble three price aluminum compound constitution membrane's skeleton, enables the membrane to have certain thickness, also its stability is high, therefore enables the membrane also to have the good intensity. The soluble six price chromium compound disperses in the membrane interior has the good packing function, when the membrane receives the abrasion, this place may cause to deactivate once more, namely has the inhibitory action to prevent the base metal to suffer the corrosion. In the salt-fog test and the tepid experiment, has the chromates epithelium's galvanization level to want high ten time of even ten time of many compared to the non-membrane coating corrosion resistance.
The different parent metal uses the different chromate treatment solution, obtains the film and the membrane ingredient is also different. But in chromic acid salt brine, Cr+6/SO4-2 ratio immediate influence membrane color and thickness, when the sulfuric acid salinity is invariable, three price chromium the content is approximately high, then forms the chromates epithelium's quantity to be many. In has not increased the acid or in the alkali chromic acid salt brine is unable to form the aluminate epithelium, must therefore obtain the thick film, must make the solution maintains the best PH value. The water used has cleaned the aluminate epithelium, cannot be dry in 5O℃ the above temperature, when is higher than above this temperature, sixth the price chromium compound in epithelium will become the insolubility by the solubility, but will reduce the self-recovery ability, will cause the film along with temperature increment to present cracking.
(3) oxidized
Soaks the steel iron stock in including in the oxidant alkazid solution, for example in the potassium nitrate or the sodium nitrate caustic soda solution, and maintains its boiling point for 140℃ about, or soaks the steel iron stock in the nitrate of soda and the potassium nitrate fused salt, after taking out, quenches in the water, may obtain good-looking black oxide compound in its surface is the ferric oxide membrane, its ingredient for the ferrous oxide and the ferric oxide mixture, is sharpens the ferrous metal corrosion prevention ability easily one kind the economical method. Steel and iron chemistry oxide film's thickness is extremely thin, generally is 0.5~1.6 μm, the corrosion resistance is limited, thickness in 2μm on membrane, the outward appearance does not have the light gloomily, assumes the black or the black gray, the film has the very good adsorbability, if soaks after the pickling oil or the coating, its anti-salt mist corrodes the performance may increase several times to several dozens times.
The steel and iron components need the oil removing and the acid pickling before the oxidized, the superficial fat are few, and the non-corrosion product's components, may admit in the thick alkazid solution to carry on the chemical oxidation directly. An oxidized is completes in one kind of tank liquor, two oxidizeds complete when the solution ingredient different two kind of tank liquor, uses an oxidized, the production film is thin, the corrosion resistance is bad. When uses two oxidizeds, the production film is thick, its corrosion resistance is also good. After oxidized's components, must pass through clean fully, then boils in the soapy water, presses is carrying on dry and spreads the oil.
