Effect of Initial Surface Finishing Roughness on Corrosion Behaviour of AISI 1050 Carbon Steel in CO2 Environment

There are different parameters which can affect electrochemical reactions such as type
of electrolyte, velocity, temperature, oxidizing agents, impurities, anode material type
and surface treatment. This research is purposely to investigate the factor that influence
the corrosion rate focuses on the mechanistic aspect of the metal itself in term of initial
surface finishing roughness which are essential to understand early-stage features of
corrosion. Surface finishing roughness of the metal was believed could affect the
hydrodynamic and mass transfer boundary layer which influenced electrochemical and
mechanical-chemical behaviour on the surface of the metal. Two main type of testing
were employed to get the corrosion rate of the tested metal which are Linear
Polarization Resistance (LPR); to measure the average current density, icorr of the
corrosion mechanism and Weight Loss Immersion; to measure the average weight loss
of the metal due to corrosion. Corrosion rate values will be calculated based on the
average current density, icorr and average weight loss and a trend in the effect of
surface roughness on corrosion resistance of mild steel was introduced. The
experiments used the samples which were abraded using silicon carbide, SiC abrasive
paper grit #80, #280 and #500 respectively. The initial surface topography of the metal
will be analyzed using Atomic Force Microscopy (AFM) to differentiate the average
surface roughness of the surface. The specimen was tested at pH 5.5, 3.5 wt. % Sodium
Chloride which react as synthetic seawater, in static flow solution purged with CO2
gas. The experimental results showed that as the surface finishing become finer, the
average weight loss of the corroded sample decreased with average decrement about
11.78% and the average of the current density, icorr of the corrosion mechanism of the
corroded sample decreased with average decrement about 10.46%. In summary, when
the surface finishing become rougher, the corrosion activity of the metal increase based
on the increment of average weight loss and current density, icorr values hence rate of
the corrosion will increase respectively