The plates used (a total of 16 samples) comprehended Steel SAE 1020 with a superficial area of 62.5 cm², acquired commercially. All of the samples were subjected to sanding with abrasive wool steel for the removal of oxide layers, degreasing with the use of neutral surfactant for laboratory cleaning, and complete drying for the removal of potential contaminants.

The solutions were comprehended in salt water (AS), obtained in the city of Guarujá SP, with a conductivity approximately of 53,000 μS/cm, and distilled water (AD) with a conductivity of 15 μS/cm. In addition, it was introduced Na₂CO₃ 5% m/m of the Kitano brand was to the AS for the simulation of the presence of CO₂ forming a new environment named ASB. Temperature variations have a significant impact on the performance of imidazoles as corrosion inhibitors, influencing both the stability of their adsorption onto metallic surfaces and the overall corrosion rate. Nevertheless, in the present study, all experiments were carried out under ambient temperature conditions, without simulating the thermal fluctuations typically encountered in offshore environments. This limitation highlights an opportunity for future research to investigate the thermal stability and efficacy of the inhibitor under more realistic operational conditions.

As a potential inhibitor (IP) it was used an imidazole antifungal drug of a lipophilic character granted by the structure (1-[(2-chlorophenyl)-diphenylmethyl]imidazole). Imidazoles are plane organic compounds, heterocyclic, aromatics with 5 members, with 2 nitrogens in their structure being one of the nitrogens pyrrole type and the other pyridine type [4] . The imidazole presents amphoteric behavior: it shows acid in the N-H bond like the pyrrole and a close basicity to the pyridine. Both molecules (imidazole and pyridine) have nitrogen as a pair of free electrons. Since it is not necessary to use these electrons to complete the system π, they can receive a proton composing an aromatic cation in an acid environment [5] . The IP was in pharmaceutical form assisting in its emulsifying process with the aqueous solution of action.

The selection of the compound was primarily based on the chemical characteristics of the imidazole ring, which features two nitrogen atoms within the aromatic system (one exhibiting pyridine-like behavior and the other pyrrole-like), both possessing lone pairs of electrons. These electron pairs are capable of forming coordinate covalent bonds with the metallic surface, thereby promoting the adsorption of the compound and creating a protective barrier against corrosive agents. The coordinate bonding between the nitrogen atoms of the imidazole and the vacant d-orbitals of the metal plays a critical role in preventing surface oxidation.

The chosen compound, an antifungal agent commonly known as clotrimazole, possesses a highly lipophilic structure (favoring interaction with hydrophobic, oxidized metal surfaces), stability in aqueous media, and additional aromatic groups (phenyl and chlorophenyl) that enhance its adsorption affinity. Its good solubility in aqueous and lipophilic environments facilitates homogeneous dispersion in the testing media. The compound was utilized in its pharmaceutical cream form, which facilitated emulsification in the aqueous solutions employed during the experiments.

Corrosion protection mainly occurs through the adsorption of imidazole molecules onto the metal surface, forming a stable barrier. This adsorption involves coordinate covalent bonding between the lone electron pairs on the nitrogen atoms of the imidazole ring and the vacant d-orbitals of iron atoms. Imidazole acts as a nucleophile and iron as an electrophile, resulting in a strong bond that prevents contact between the metal and corrosive agents such as O₂, H₂O, Cl⁻, CO₂, and H₂S. The effectiveness increases under low temperatures, on partially charged surfaces, and in the presence of aromatic groups, which enhance the adsorption area and lead to a denser protective layer [6] .

The analytic process consisted of the mass assistance in the oxide formation in the subjected samples to different aggressive aqueous environments for the verification of the influence of outside factors (like salinity) which were evaluated through the evolution of corrosion rates. It used the IP in order to notice its possible protective and or inhibitory action on the process. Saltwater with high electrical conductivity (~53,000 µS/cm) was used, close to the typical salinity of marine environments. The presence of CO₂ was simulated by adding sodium bicarbonate, which represents one of the common corrosive agents in offshore oil environments. The study incorporated control samples without the addition of the inhibitor for each testing condition. These control samples established the baseline corrosion rates, enabling a systematic comparison and quantification of the imidazole’s inhibitory effectiveness. The results demonstrated substantial reductions in corrosion rates, thereby validating the inhibitor’s protective performance.

After the samples were properly sanded, degreased, and dried, they were weighed in an analytical balance and completely immersed, in duplicates, in solution (with and without inhibitor), and remained under rest for the seasonal assistance of corrosion rate. For each measurement, it was realized that a sanding and superficial cleaning of the sample was performed, removing the oxide layer, and it obtained information about the mass of each piece.

Each duplicate was held in a glass jar hermetically closed previously cleaned and dried, removing impurities presented, with the exception of the AR sample, which was exposed to air during the period. The samples that contained liquid were held closed during the procedure, while the samples that didn’t contain liquid as a corrosive agent were held open during the process. Table 1 shows the organization of the samples.

The corrosion rate expresses the speed of abrasion verified on the steel surface. The correct evaluation of the corrosion rate is, in a general way, of great importance for the determination of the lifespan of the equipment and industrial installations [7] .

The corrosion rate can be calculated following the rule ASTM G31-72, through the following Equation:

$mpy=\frac{834\times \Delta m}{s\times t\times \rho }$

Where:

mpy = Is the loss of thickness, (thousandth of an inch per year);

Δm = Lost of mass (mg);

s = Exposed area, (in²);

t = Time of exposure (h);

ρ = Density of material (g/cm³).

The ASTM G31-72 standard was selected due to its status as an internationally recognized guideline for: conducting immersion corrosion tests of metals and alloys in aqueous solutions; determining corrosion rates based on mass loss (gravimetric method); and establishing standardized conditions for sample preparation, testing procedures, and result calculation to ensure comparability. The present study aimed to evaluate corrosion behavior in simulated offshore environments using static exposure, aqueous solutions, and monitoring over a period of 46 days. These experimental conditions align closely with the scope for which ASTM G31-72 was designed, namely, controlled laboratory immersion corrosion testing. Furthermore, employing this standard legitimizes the methodology used to assess the efficiency of imidazole as a corrosion inhibitor, providing a widely accepted framework for evaluating improvements in corrosion resistance.