Deposition of internal surface coating for anti-corrosion purpose

Deposition of internal surface coating for anti-corrosion purpose

Long metallic tubes are widely used in the process industry for a vast range of liquids. A major drawback is the appearance of corrosion, thus, making necessary the development of tube protective surfaces, as for example thin film coatings. Those metallic tube coatings have for long mainly been a subject for CVD processes. However by recent research within the area of PVD plasma coatings using sputtering with coaxial magnetrons, it is now possible to obtain a wide variety of materials and alloys, typically non accessible with other techniques and with superior coating properties as for example tungsten (W) or Titanium Nitride (TiN).

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Nano4Energy has developed a method of depositing a multilayer thin film corrosion barrier combining Titanium with TiN in tube internal surfaces. A multilayer film with a controlled nitrogen gradient along the film thickness is deposited in steel tubes in order to obtain a coating with maximum adhesion, density and wear resistance, without sacrificing the corrosion properties. Moreover, the multilayer film residual stresses are well controlled as a consequence of a smooth transition to compressive surface stresses. To perform this, a new sputtering technique, called HIPIMS (High power impulse magnetron sputtering) was implemented to achieve improved film adhesion and enhanced density and stability as compared with CVD or other PVD coating technique. This technique allows control of the grain structure and composition at the atomic scale, also with the possibility to grow amorphous structure to eliminate the risk of inter-granular corrosion.

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