**5. Key results**

328 Corrosion Resistance

in Marble's solution (4 g CuSO4 + 20 ml HCl + 20 ml distilled water). The schematic picture

The specimens were further characterized by microhardness indentation, elemental analysis by FESEM and X-ray diffraction (XRD) analysis using Cu-Kα radiation. Tribological properties were evaluated with a Taber® Linear abraser model 5750 dry slide tribo-tester using an 5-mm diameter AISI 316L collet nut as mate material. The stroke length applied was 25.4 mm under a constant load 600 g. After 3600 cycles of sliding (completed in 60 minutes) having maximum velocity of 79.76 mm/sec, the specimen wear loss was measured by balance to evaluate cumulative weight loss. Microstructures of treated layers were investigated by X-Ray diffraction analysis (XRD) using Cu-Ka (40 kV, 150 mA) and Field Emission Scanning Electron Microscopy (FESEM). The electrochemical corrosion behaviour of the as-treated surfaces was evaluated by measuring the anodic and cathodic polarisation curves in aerated 3.0 % NaCl solution at a scan rate of 1 mV/min. The tests were conducted at room temperature by using a three electrode potentiostat with a computer data logging, requisition and analysis system. Potentials were measured with reference to the standard

Corrosion tests were performed electrochemically at room temperature in a flat cell with 3.0% NaCl in distilled water. The flat cell, as schematically shown in Fig. 5, was a threeelectrode set-up consisting of a saturated calomel reference electrode (SCE), a platinum auxiliary electrode and a working electrode (sample). Sample to be tested was placed against a Teflon ring at one end of the flat cell, leaving a theoretical circle area of 67.5 mm2 on the sample surface in contact with the testing solution through a round hole in the Teflon ring. Test control, data logging and data processing were achieved by a ''Sequencer'' computer software. The scanning potential was in the range of -0.5 to + 1.4 V, and the scan rate was 1 mV/s. From the polarization curves, the average values of the corrosion potential (Ecorr), the corrosion current density (Icorr) and the polarisation resistance (LPR) were

Fig. 5. Schematic diagram of the flat cell used for polarization corrosion test (Li &

of fluidized bed furnace is shown on Fig. 4.

calomel electrode (SCE).

calculated.

Bell, 2004).
