The Pt/C catalyst shows a Tafel slope
of 31.2 mV dec-1, which is consistent with the reported values [11,26].
The Tafel plots of the MoP and MoP@ MSN catalysts are displayed in Figure 4(b), which were fitted to the Tafel equation (Z = b log j + a, where j is the current density and b is the Tafel slope
), yielding the Tafel slopes
of 100 and 341 mV for MoP@MSN and pure MoP, respectively.
The corrosion of magnesium sacrificial anode with AC interference is biased towards cathodic control in the first two days because the Cathodic Tafel Slope
is bigger than the Anode Tafel Slope
In acidic solutions, the Tafel slope
amounts to 30 mV/dec (1M [H.sub.2]S[O.sub.4] at 30[degrees]C ), 42mV/dec (1M [H.sub.2]S[O.sub.4] at 20[degrees]C) , and 30-50 mV/dec in 0.5 M [H.sub.2]S[O.sub.4] at room temperature .
The values of cathodic Tafel slope
[beta]c and anodic Tafel slope
[beta]a were found to change with increasing inhibitor concentration, which indicated that the inhibitors control both anodic and cathodic reactions .
Namely, the Tafel slope
on Pt(Bi)/GC electrodes is about 120 mV [dec.sup.-1], indicating that the HCOOH oxidation takes place on a surface almost free of C[O.sub.ad] through dehydrogenation path.
The corrosion potential [E.sub.corr], corrosion current [I.sub.corr], anodic Tafel slope
([b.sub.a]) and cathodic Tafel slope
([b.sub.c]) calculated using Tafel extrapolation method, are compiled in Table VI.
where P is the total porosity, [R.sub.pol] and [R.sup.*.sub.pol] are the polarization resistances of bare and coated mild steel, [DELTA][E.sub.corr] is the corrosion potentials differences of bare and coated mild steels, and [b.sub.a] is the anodic Tafel slope
for bare mild steel.
The different corrosion parameters are anodic Tafel slope
(ba), cathodic Tafel slope
([b.sub.c]), corrosion current density ([I.sub.Corr]), and corrosion potential ([E.sub.Corr]).
where, [E.sub.pc] = cathodic peak potential, volt (V), [E.sub.1/2] = half wave potential (V), D = diffusion coefficient([cm.sup.2]/s), b = Tafel slope
= 2.303 RT / [alpha] [N.sub.a] F ; [alpha] = transfer coefficient, [N.sub.a] = number of electrons involved in the rate determining step, R = molar gas constant =8.314 joul/K/mol, T = temperature ([o.sup]K), v = scan rate (V/s) and [k.sub.f] = charge transfer rate constant (cm/s).
Where, [[beta].sub.a] = Anodic Tafel slope
, [[beta].sub.c] = Cathodic Tafel Slope
, [R.sub.p] = Polarization Resistance,
However, the effects of electrochemical reduction of rust on both the Tafel slope
and the corrosion rate induced from Tafel extrapolation were different among both alloys and immersion periods.