(ii) Very negative values of corrosion potential
from -400 mV to -600 mV were recorded showing an active corrosion process of the steel reinforcement.
In formula (4), [R.sub.ps] and [R.sub.pc] are the polarization resistance of the substrate and the coating coated substrate, respectively, [DELTA][E.sub.corr] is corrosion potential
difference between the epoxy-lacquer based coating and tinplate, and [[beta].sub.at] is the anode Tafel constant of the tinplate.
This type of attack occurs only on materials that work at a potential (corrosion potential
, [E.sub.corr]) higher than a certain critical value, which is known as the pitting potential ([E.sub.pit]) and depends on the composition of the metallic material.
The corrosion current density ([i.sub.corr]) and corrosion potential
([E.sub.corr]) are obtained from the intersection point of anodic and cathodic current curves.
It showed that OTS SAMs have good corrosion resistance, and the corrosion potential
of copper OTS SAMs protection increased by about 1.02 V, while the corrosion current density decreased to 0.59 A/[micro]A/[cm.sup.2].
The corrosion potentials
([E.sub.corr]) and corrosion current density ([i.sub.corr]) are obtained as a result of the test and then the corrosion rate measurement is obtained by using the following equation :
It provides information on the corrosion behavior of the system based on the steady-state corrosion potential
The corresponding corrosion potential
and corrosion current density of each sample under different pH are listed in table 2.
In the polarization current experiments, the potential was scanned from -100 mV below to +100 mV above the corrosion potential
[E.sub.corr] at a scan rate of 2 mV [s.sup.-1].
SVET experiments were performed to measure the current density distribution between the rivet head of interest and surrounding magnesium for the geometric situation illustrated in Figure 6 (a), throughout the volume defined by the bi-metal/electrolyte interface at its free corrosion potential
The first group was subjected to four electrochemical techniques: corrosion potential
, linear polarization resistance, Tafel curves, and electrochemical impedance spectroscopy, applying a 24 factorial experimental design with six replicates at random, for a total of 22 samples, where the following variables were studied: concentration of fluoride, pH, applied force, and immersion time.
Once the half-cell potential was obtained, we used the linear polarization resistance (LPR) method to get the measurement parameters, such as the corrosion potential
(Vcorr), polarization resistance (Rp), and corrosion current (Icorr), in accordance with ASTM standard G59.