First, clearly that seamless steel pipe passivation of metal phase and solution phase is caused by the interfacial phenomena. It has been studied mechanical abrasion in the passive state on the influence of a metal. Experimental results show that measured continuously when the metal surface abrasion, the electric potential of the metal in the negative direction intense, that is, trimming the metal surface in the passive metals can cause activation. Certifying that the phenomenon is an interface passivation phenomenon. It is in certain conditions, steel plant contact between metal and dielectric changes the interface. Electrochemical anodic passivation is the metal and the potential change on the electrode surface to form a metal oxide or salts. These substances covered tightly with the metal surface passivation film on a metal deactivator result. Chemical passivation is an oxidizing agent such as concentrated HNO3 direct the action of the metal oxide film formed on the surface, or added easily passivated metal such as Cr, Ni, etc. caused. Chemical passivation, adding the oxidant concentration is not less than a critical value, otherwise not only will not lead to a passive state, the counter will cause the metal faster dissolution. Precision steel surface passivation film there are mainly two theories, Serve phase film theory and adsorption theory. A phase film theory, when the metal dissolved, in the passive condition, tightly formed on the surface, good coverage of solid substances which form a separate phase, known as a passivation film or said phase film this film is the metal surface and the solution was mechanically isolate the metal dissolution rate substantially reduced, and blunt -stated. Experimental evidence in some passivation of the metal surface, can be seen the presence of a phase film, and to measure its thickness and composition. Such as the use of a metal capable of dissolving the oxide film does not work with the reagents dissolve and remove carefully the metal film, can be seen isolated from the passivation film, the passivation film is formed when the metal anodic dissolution, and its surrounding solution near layer component changes. On the one hand, dissolved metal ions due to diffusion down fast enough ( dissolution speed ) varies accumulation. On the other hand, the interface layer of the hydrogen ions migrate towards the cathode but also the solution of the anion ( including OH-) migrate towards the anode. Result, there are OH-ions near the anode, and other negative ions enrichment. Precision steel elastic deformation, the construction of improper operation easy to make thick steel vertical deformation even greater instability, seriously impairing its functionality. Therefore, when producing thick-walled steel equipment after the end of the pipe must be pre- disposal equipment selection, good to recite familiar plastic pipe production did not pass the required quality selection of Canon contentment request pretreatment equipment.
Waterfall curtain coating method is evaluated silty large and easy to form a thick coating, especially suitable for thick-walled steel pipe in plastic, coating thickness up to 1mm or less. Mount vibration friction vibration corrosion effect due damaged thick steel protective film, bare metal rapid oxidation, wear and oxidation are repeated, increasing the damage. In addition, the precision steel metal surface due to pressure generated cold welding or melting and subsequently due to the relative motion of the metal nibs off, and rapid oxidation. Both oxidation rust tablets, destroying metal interface. Oxygen corrosion in Mount vibration is very important, but also some friction vibration corrosion without oxygen. Protective coating method can grease the contact surfaces, friction can be reduced, oxygen side, while if the surface is more efficient phosphate, which can also use carbide, shot blasting or cold in order to improve the surface hardness.
