The Effect of Creating Different Size Surface Patterns on Corrosion Properties of Nickel

Materials Characterisation VII

2015

Unidirectional surface roughness of varying magnitudes were created on both nickel and mild steel by grinding on SiC papers with grit sizes from G60 (roughest) to G1200 (smoothest) and the corrosion resistance in 0.5M H 2 SO 4 solution was determined using a potentiodynamic polarization technique. A different trend of corrosion rate versus roughness was seen for the active-passive metal (nickel) and non-active-passive metal (mild steel). For nickel there was an increase in corrosion rate with increasing roughness, whereas for mild steel the corrosion rate decreased with increasing surface roughness. Furthermore, through a detailed examination of the surface before and after corrosion using techniques including profilometry, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), it was established that different corrosion mechanisms were operative for nickel and mild steel. For both metals, the smaller grit sizes produced a rougher surface with wider and deeper grooves. In the case of nickel, the higher roughness provided a greater contact area between the corrosive medium and metal and there was trapping of the corrosive ions in the deep grooves. Both of these factors would lead to an increase in corrosion rate. Also, for the smoother nickel surfaces, it is easier to form a stable passive film. For mild steel, which does not form a passive film, corrosion rates are generally much higher than for nickel. For the rougher surfaces with the deeper grooves, the corrosion product, FeSO4, can fill the grooves thereby acting as a barrier to further ingress of the corrosive ions to the un-corroded metal.

Section: Eds Analysismentioning

confidence: 86%

Simultaneous effect of surface roughness and passivity on corrosion resistance of metals

Materials Characterisation VII

2015

“…This is also in agreement with the measured corrosion rate values. In this case, no severe corrosion has occurred, mainly due to the existence of heterogeneous wetting [15].…”

Section: Scanning Electron Microscopymentioning

confidence: 86%

“…The main mechanism behind the significant decrease in the corrosion rate has been shown to be heterogeneous wetting [15,16]. Heterogeneous wetting results in formation of alternating solid/liquid zones and stable air/vapour pockets.…”

Section: Corrosion Testingmentioning

confidence: 99%

“…The air/vapour pockets allow the formation of the passive oxide layer but prevent its dissolution by the electrolyte. The heterogeneous interface, formed between the solution and the surface, significantly decreases the overall contact area between the surface and the electrolyte, thus significantly decreasing the corrosion rate [15,16]. …”

Section: Corrosion Testingmentioning

confidence: 99%

See 1 more Smart Citation

The effect of different surface topographies on the corrosion behaviour of nickel

WIT Transactions on Engineering Sciences

2013

The electrochemical and corrosion behaviour of a surface is extremely complicated and depends on various chemical, physical and mechanical factors. In this study the effect of different surface roughnesses on the corrosion resistance of nickel in 0.5 M sulphuric acid was investigated. Open circuit potential, corrosion current density, polarization resistance and corrosion rate were measured for surfaces polished with different grits (120, 240, 400, 600 and 1200) of silicon carbide papers. The surface roughness was measured using a profilometry method both before and after corrosion testing. SEM images were taken and compared for all of the samples before and after corrosion tests. The results showed that surface roughness and surface morphology can considerably change corrosion and corrosion rate. A higher corrosion resistance is obtained for surfaces with lower roughnesses. Finally, the results were compared with specimens where a specific surface patterning was obtained using a laser ablation method.

“…In the case of metals such as aluminium and nickel, the lower corrosion rate was related to the formation of a stable passive film on smoother surfaces as suggested by the authors [3,[13][14][15][16] but in the case of mild steel no stable passive film is formed and rougher surfaces showed less corrosion and lower oxygen content. Generally, more increase in the oxygen content was observed for mild steel indicating more oxides form on the surface.…”

Section: Eds Analysismentioning

confidence: 88%

Simultaneous effect of surface roughness and passivity on corrosion resistance of metals

WIT Transactions on State-of-the-Art in Science and Engineering

2017

Unidirectional surface roughness of varying magnitudes was created on both nickel and mild steel by grinding on SiC papers with grit sizes from G60 (roughest) to G1200 (smoothest) and the corrosion resistance in 0.5 M H 2 SO 4 solution was determined using a potentiodynamic polarization technique. A different trend of corrosion rate versus roughness was seen for the active-passive metal (nickel) and non-active-passive metal (mild steel). For nickel, there was an increase in corrosion rate with increasing roughness, whereas for mild steel the corrosion rate decreased with increasing surface roughness. Furthermore, through a detailed examination of the surface before and after corrosion using techniques including profilometry, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), it was established that different corrosion mechanisms were operative for nickel and mild steel. In the case of nickel, the higher roughness provided a greater contact area between the corrosive medium and metal and there was trapping of the corrosive ions in the deep grooves. Both of these factors would lead to an increase in corrosion rate. Also, for the smoother nickel surfaces, it is easier to form a stable passive film. For mild steel, which does not form a passive film, corrosion rates are generally much higher than for nickel. For the rougher surfaces with the deeper grooves, the corrosion product, FeSO4, can fill the grooves thereby acting as a barrier to further ingress of the corrosive ions to the un-corroded metal.