THIN NICKEL LAYER BEHAVIOUR IN NATURAL SEA WATER

Abstract

Various methods were used, in order to protect the material base; the study subject has been put under various conditions and were thus implemented in an attempt to prolong the operating life and to require less maintenance and replacement of parts. Pulsed laser deposition method was used to cover a S 235 carbon steel sample with a thin nickel film, using laser ablation and thus obtaining a protective layer, offering increased corrosion resistance. S 235 carbon steel samples were covered on a single face with thin films. The material used for laser ablation is nickel. The samples were immersed for 126 days in static seawater at ambient temperature and were individually weighted on the analytic balance at different time intervals, in order to determine the corrosion process speed. The study was performed by employing the gravimetric method. Through the corrosion research process using the gravimetric method, the parallelepiped samples covered with Ni using pulsed laser deposition were immersed 126 days in static sea water at environment temperature. The corroded surfaces, after being submerged in seawater, were investigated using optical microscopy and atomic force microscopy. Atomic force microscopy investigations performed on long-term corrosion-tested samples highlight areas with compact and homogeneous surfaces that did not allow the corrosive agent to interact with the base material, a fact confirmed by optical metallographic analysis. Wave mode images show discontinuities of surface-deposited incipient corrosion points that are possible pathways of the corrosive agent to the sample material. The analysis made on one side thin film covered sample, after a long term corrosion test, using atomic force microscopy investigation and gravimetric test, shows the rate of corrosion, the discontinuities of the surface and the corrosion pitting in the material. Evaluating the method of thin film deposition layer leads to the obtainment of high reliability and low cost material parts using this method. The corrosion rate is established, remains constant and protection of the material base is achieved.