Corrosion Rate Of Aluminum Research Articles

Effect of spinach (Spinacia oleracea) leaf extract on the aluminum (Al) as a green corrosion inhibitor in HCl medium

Green corrosion inhibitors have recently attracted much attention due to their non-toxic properties, especially plant extracts. This study used spinach leaf extract (Spinacia oleracea) as a corrosion inhibitor on aluminum in an HCl medium. Spinach leaf extract (Spinacia oleracea) was obtained by maceration method, using ethanol as the solvent, which was then distilled to purify the extract. The corrosion inhibition properties were studied by the gravimetric method. The results showed that spinach leaf extract (Spinacia oleracea) can efficiently decrease the corrosion rate of aluminum in an HCl medium, achieving a maximum efficiency of 96.7742 %. Spinach leaf extract (Spinacia oleracea) formed a protective layer on the aluminum surface via adsorption and chemisorption, thus increasing surface coverage and blocking mass transfers. As the inhibitor concentration increases, the corrosion rate decreases, and the corrosion inhibition efficiency increases. This study shows that spinach leaf extract (Spinacia oleracea) is a viable organic corrosion inhibitor option with high efficiency.

Study on the crystallographic orientation dependent electrochemical corrosion rates of aluminum and its binary alloys

This paper provides a study for crystallographic orientation-dependent corrosion rate of aluminum employing an ab initio model with inputs from first-principles calculations. Results showed that the sequence of corrosion rate is in the order of (111) < (410) < (331) < (221) < (321) < (211) < (110) < (100) < (210) < (320) < (310) < (311) for aluminum. The predicted corrosion current densities for (111), (110), and (100) surfaces are in general agreement with the experimental results. The alloying effects were further investigated employing this model with results validated via the polarization curves of alloyed aluminum.

Research on Metal Corrosion Behaviour of Indirect Air-cooled Circulating Water System

Abstract The indirect air cooling system of an air-cooled power plant consists of a surface condenser and an aluminum radiator. The radiator is usually made of 1050A pure aluminum, and the circulating water pipe connecting the radiator is made of Q235B carbon steel. This article simulates and controls typical water quality parameters such as dissolved oxygen and pH value in indirect air cooling systems using a self-designed simulation device, and studies the influence of various water quality parameters on material corrosion behavior in intercooled circulating water systems when aluminum and carbon steel coexist. The results indicate that factors such as dissolved oxygen, conductivity, pH value, temperature, and redox potential can all affect the corrosion rate of carbon steel and aluminum materials; The increase in temperature and dissolved oxygen leads to an increase in corrosion rate; The main way carbon steel corrodes the system is by consuming dissolved oxygen; The corrosion behaviour in the water circuit will lead to an overall decrease in pH value. In the presence of multiple metals, the influence of iron ions in the solution significantly increases the corrosion rate of aluminum.

The Effectiveness of a Combination of Lime (Citrus aurantifolia.), Lerak (Sapindus rarak) and Jasmine Flower (Jasminum nudiflorum) Extracts as and Environmentally Friendly Corrosion Inhibitor

Corrosion can also be defined as the forced destruction of metal by the surrounding medium which is usually a liquid (corrosive agent). Corrosion prevention processes can be carried out, including by coating the metal surface, cathodic protection, adding corrosion inhibitors and so on. Several types of inhibitors that have been widely used in industrial applications are synthetic chemical inhibitors. However, the compounds of inhibitors are environmentally unfriendly, toxic and expensive. To overcome this problem, it is necessary to develop an environmentally friendly alternative corrosion inhibitor or better known as a green inhibitor. This research aims to test the effectiveness of using a combination of lime (Citrus aurantifolia.), Lerak (Sapindus rarak) and jasmine flower (Jasminum nudiflorum) extracts as an environmentally friendly corrosion inhibitor. The results obtained were inhibitors in the form of a combination which were added to the corrosive medium HCl which could reduce the rate of aluminum corrosion. This research also shows that time and concentration influence the corrosion rate. A higher concentration (200 ppm) has a greater inhibitory power than a concentration of 100 ppm. The best inhibitory power is found in 200 ppm inhibitor with a soaking time of 20 minutes

The role of the oxide layer in the corrosion of aluminium in acidic solutions

AbstractThe role of the oxide layer in the corrosion of aluminium in hydrochloric, sulphuric(VI) and orthophosphoric acid is studied at pH 1. The oxide layer is stable in hydrochloric and sulphuric acids. The corrosion rate of aluminium in these solutions is 0.2 and 0.3 mm/year, respectively. The oxide layer is unstable in orthophosphoric acid and the corrosion rate is higher, 1.75 mm/year. The corrosion process is studied using scanning electron microscopy, immersion and electrochemical techniques. The mechanism of corrosion of aluminium in the orthophosphoric acid solution is proposed. It includes the adsorption of a reaction intermediate on the surface of the corroding metal and the formation of the oxide layer at anodic potentials with respect to the open‐circuit potential. It is also explained when the inductive loop appears on the electrochemical impedance spectra of aluminium corroding in orthophosphoric acid solution. The mechanism of aluminium corrosion in hydrochloric and sulphuric acid is more complex compared to orthophosphoric acid, and is not analysed in detail.

Corrosion inhibitory studies of an eco-friendly thiourea derivative of amino acid on aluminium using 0.1M HCl solution

The inhibition efficiency and corrosion rate of aluminium were investigated at varying temperatures and immersion time using thiourea complex with an organic ligand at concentrations of 0.20, 0.40, 0.60, 0.80 and 1.00 M. The results showed that an increase in the concentration of the complex thiourea led to an increase in the inhibition efficiency, which was attributed to the availability of the proton moiety of the thiourea lost as electron in acidic media. The inhibition efficiency decreased as the immersion time increased with temperature and the largest decrease observed at 333 K due to the distortion of molecular structure of the complex thiourea at high temperatures. The corrosion rate decreased with an increase in immersion time but increased with temperature, possibly due to inhibitor molecular rearrangement. The activation energy of the suppression process of high-concentration thiourea was found to be higher than that of low-concentration, indicating that the adsorption process was triggered by physical adsorption. The formation of a thin film on the metal surface was due to the presence of complex thiourea acted as a barrier to both energy and mass transport, leading to an increase in the activation energy. The adsorption of the thiourea derivatives complex on aluminum was primarily physisorption. The Langmuir, Flory-Huggins, Tempkin, and Dubinin-Radushkevich adsorption isotherm models were investigated with Langmuir found to be the most fitted model based on high R2 values of the model.

Effect of anodizing on aluminum alloy 2024 with boric sulfate acid in medium 3.5 % NaCl

The utilization of metal materials finds widespread applications in various industries, including the aircraft industry, where aluminum alloys are commonly employed. However, metal materials are prone to corrosion under specific conditions, necessitating the implementation of corrosion prevention methods to decelerate the material's corrosion rate. Corrosion is a process in which the quality of metal deteriorates due to environmental influences. An effective approach to inhibit corrosion is through anodizing, which involves applying a protective coating to the metal surface, preventing direct contact with the surrounding environment. In this research, the focus was on studying the corrosion rate of aluminum alloy 2024 using Boric Sulfate Acid Anodizing (BSAA) at 10 volts and immersion times of 10, 15, and 20 minutes, followed by sealing with acetic acid in a corrosive environment containing 3.5 % NaCl. The main goals were to evaluate the effectiveness of anodizing with and without sealing in lowering the rate of aluminum corrosion, to compare the effectiveness of anodizing with and without sealing, and to create adsorption models using Langmuir adsorption. Through the examination of the potentiodynamic approach, it was shown that anodizing had an inhibitory impact that was strengthened by sealing. The maximum efficiency of 76 % was attained after 20 minutes of anodizing and sealing at 10 volts. A correlation value of 0.7487 from the Langmuir adsorption modeling was also obtained, pointing to an advantageous adsorption behavior. This research demonstrates how effectively anodizing for aluminum alloy 2024 works with and without sealing, especially in a 3.5 % NaCl-corrosive environment

Investigating the potential of casein as a sustainable material in inhibiting the corrosion of aluminum in hydrochloric acid

AbstractIn this study, the efficiency of casein in inhibiting the corrosion of aluminum in 0.1 M HCl was evaluated. Based on the weight loss data, increasing the amount of casein in the electrolyte from 50 to 500 ppm at 298 K decreased the corrosion rate of aluminum, for instance, from 2.53 to 0.58 g m−2 h−1. It was also demonstrated that with casein, the activation energy of the corrosion phenomenon increased (e.g., from 6.52 kJ/mol without casein to 27.54 kJ/mol with 500 ppm casein). The electrochemical polarization studies illustrated that in the presence of 500 ppm casein, the corrosion current density remarkably decreased from 63.09 to 6.1 µA/cm2. This was compatible with the increase in the charge transfer resistance recorded by electrochemical impedance spectroscopy. Furthermore, the X‐ray photoelectron spectroscopy and atomic force microscopy techniques confirmed the adsorption of casein on the working electrodes, which caused an enhancement in the surface quality of the specimens.

Double side friction stir welding effect on mechanical properties and corrosion rate of aluminum alloy AA6061

Friction Stir Welding (FSW) is a solid-state welding method that has diffusion and different metal structures can blend well. Friction stir welding (FSW) has a weakness, one of which is the lack of flexibility the welding process is only carried out on one side of the plate being welded, so it is not applied on thick materials. Double side friction stir welding is a double working process in which the plate to be welded is subjected to friction from two tools on opposite sides. In the DS-FSW welding process, the dimensions and geometry of the tool and pin greatly affect the quality of the joint. This study to determine the mechanical properties and corrosion rate of Double side friction stir welding aluminum 6061 with variation rotation speed and axis of top and bottom tools. The results of this radiographic test can be seen that specimen 4 welded with variations in speed and tool position has defects in the form of incomplete fusion (IF). The results of microstructural observations showed that the heat caused by the welding process resulted in recrystallization in the form of fine grains in the stirring area and there was no phase change. The highest hardness value in the welding area is specimen B. The largest bending value at the 1G welding positions is specimen D, which is 41.86 MPa with a strain value of 13.23%, while the smallest value at the 4G welding position is specimen A, which is 38.18 MPa with a strain value of 5.03%. The fracture and crack surfaces showed that crack initiation, propagation and material stirring failure occurred in all test specimens, even though the impact test specimen was cut in a small area of Incomplete Fusion, but the test results showed that there was still a surface of the parent metal that had not been stirred. The corrosion test method uses three electrode cells with corrosion media as a substitute for seawater with a salinity of 3.5% NaCl, result of corrosion test is specimen B at the 1G welding position has the highest corrosion rate value of 0.63856 mm/year and specimen An at the 1G welding position has the lowest corrosion rate of 0.058567 mm/year.

Evaluation of expired linezolid and norfloxacin drugs as proficient environmentally safe inhibitors for mitigation of aluminum corrosion in sodium chloride medium

This paper highlighted how the expired linezolid and norfloxacin drugs can inhibit the corrosion of aluminum in 1.0 M NaCl. Chemical, electrochemical and microscopic tools were employed. The calculated inhibition efficiencies (% IEs) of the drugs were raised with their concentrations. The corrosion rate of aluminum was increased with rising [NaCl] and the% IEs were increased with the drugs’ concentration and reduced with rising temperature. The acquired higher% IEs were ascribed to strong adsorption of the drugs’ molecules on the aluminum surface and such adsorption was agreed with Langmuir isotherm. Thermodynamic and kinetic parameters were calculated that confirm the mechanism of physical adsorption. The used expired drugs behaved as mixed-kind inhibitors with cathodic priority. The kinetics and mechanisms of corrosion of aluminum and its inhibition by such drugs were explained. The gained results regarding to% IEs illuminated a good concordance between all utilized techniques.

Gallic Acid as a Potential Green Corrosion Inhibitor for Aluminum in Acidic Solution

Plant extracts are intensively studied as green corrosion inhibitors of aluminum. Because these extracts are complex systems, the influence of their individual constituents on the corrosion of aluminum should be determined. In this work, gallic acid was tested for the first time as a corrosion inhibitor of aluminum in orthophosphoric acid aqueous solution. So far, its potential inhibiting properties in acidic solutions were only suggested based on promising results obtained for various plant extracts. Evaluation of the potential inhibiting properties of gallic acid was performed using electrochemical methods. The corrosion potential, polarization curves, and impedance spectra of aluminum in 0.5 M orthophosphoric acid, at T = 303 K, were determined. The corrosion potential, corrosion current density, and corrosion rate of aluminum in orthophosphoric acid were equal to −1.151 V vs. Ag|AgCl (3M KCl) reference electrode, 36 μA∙cm−2 and 0.39 mm∙year−1, respectively. These values did not change with the addition of gallic acid. The results obtained show that gallic acid does not inhibit aluminum corrosion. UV-Vis absorption spectra of gallic acid solutions and quantum mechanical calculations show that this organic compound did not adsorb onto the aluminum surface under the studied conditions.

Tannins as interphase corrosion inhibitors for aluminum in near‐neutral chloride solutions

AbstractThe addition of tara and quebracho colorado tannins remarkably reduces the corrosion rate of aluminum in near‐neutral and naturally aerated NaCl solutions. The experimental results (potentiodynamic polarization curves, corrosion potential measurements, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy [SEM‐EDS] analysis on exposed surfaces) show that both tannins behave as a mixed‐type corrosion inhibitor of aluminum. In the absence of tannins, the SEM‐EDS analysis of the exposed samples demonstrates the accumulation of corrosion products and the existence of chlorinated compounds adsorbed on the metal surface. In the samples immersed in both tannins solutions, a more homogenous and compact layer is formed over the aluminum surface. Furthermore, in these layers chlorine was not found, revealing a high blocking capacity of the chloride adsorption when the tannins are present. Taking into account these findings, an inhibitory mechanism of aluminum corrosion is proposed. This mechanism is interphase inhibition, which involves the adsorption and incorporation of tannin molecules during the corrosion products passive layer formation, resulting in a protective three‐dimensional structure that retards both anodic and cathodic reactions.

Inhibitory action of xylenol orange on aluminum corrosion in hydrochloric acid solution

The inhibition effect of xylenol orange on the corrosion of aluminum (2S Grade) in 0.4-0.6 M HCL over the temperature range 313-333K has been studied. Both thermodynamic parameters and kinetic parameters with the inhibition effect have been correlated. The inhibition efficiencies of xylenol orange are investigated by weight loss and potentiodynamic polarization methods. The corrosion rate of aluminum decreases with increasing inhibitor concentrations and the efficiency of inhibition increases with increasing concentration of inhibitor up to almost 87% in 0.4M HCL and up to 84% in 0.6M HCL. The concentrations of inhibitor have been kept in the range 2-8 mM. It is also observed that the inhibition efficiency decreases with increasing HCl concentration and temperature. The adsorption of inhibitor on the aluminum surface obeys the Langmuir adsorption isotherm equation. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic parameters. The experimental data have been successfully related with adsorption theory and kinetic equations. Polarization curves show that xylenol orange is a mixed-type inhibitor in hydrochloric acid.

Concentration Dependent Effects of Green Inhibitors on Gravimetric Indices of Corrosion Linked Metal Integrity

The use of plant phytochemicals as anti-corrosion agents is gaining widespread acceptance. This study was designed to evaluate the concentration dependent effects of green inhibitors from Pennisetum purpureum (elephant grass) Mangifera indica (mango leaves) and Heveabrasiliensis (rubber leaves) on some gravimetric indicators of corrosion linked metal stability. The material strength, weight loss, corrosion rate of the metal coupons and the inhibition efficiency of the green inhibitors were determined after 3 days. Our findings revealed a slight increase (p=0.05) in material strength (MS) of Pennisetum purpureum inhibitor treated - iron and steel at 100% inhibitor relative to their controls (minus Pennisetum purpureum -iron and steel coupons) and also relative to the (+Mangifera indica inhibitor and + Heveabrasiliensis -treated iron and steel coupons at 50% concentration. The material strength for P. purpureum-treated aluminium was slightly increased (p&gt;0.05). There was also a slight decrease (p&gt;0.05) in the weight loss of P. purpureum exposed iron coupon at a 100% inhibitor when compared to the controls, 50% P. purpureum exposed iron coupon and at 50 and 100% H. brasiliensis and M. indica-treated iron coupon in 15% acid medium. Pre-treatment of test metals with the combined green inhibitors at 50 and 100% concentration caused a significant (p≤0.05) decreases in weight loss and increases in material strength of all three test metals when compared to their respective inhibitor-free controls, and when treatment was done with a single green inhibitor. There was a slight decrease in the corrosion rate of iron, aluminium and steel coupons in acid medium treated with 50% P. purpureum inhibitor when compared to the same parameter of other green inhibitors evaluated in this study, albeit, the reduction was not significant (p&gt;0.05). There was a further decreases (p≤0.05) in the corrosion rate of iron and steel when the combined green inhibitors at 100% concentration(+All green inhibitors (PAGI) at 100%) were used relative to when treatment was done using individual green inhibitors separately. The inhibition efficiency of the combined green inhibitors at 50% concentration on aluminium, iron and steel was 86% 57% and 60% respectively. While the treatment of the same coupons with combined inhibitors (+PAGI at100% concentration) increased the inhibition efficiency to 88% 75% and 74% for aluminium, iron and steel respectively. Overall, the study revealed the possible anti-corrosion effects of the extracts of H. brasiliensis, P. purpureum and M. indica on aluminium, iron and steel coupons and the synergism in anti-corrosion characteristics of these green inhibitors when combined. This study establishes the anticorrosion effects of H. brasiliensis, P. purpureum and M. indica extracts.

Tetrahydro-dibenzo[a,d] Annulene-5, 11-Dihydrazone and Magnesium Oxide Used to Control the Corrosion of Aluminium in Chloride Ions Environment

Chloride ions interact with aluminium in marine atmosphere to form corrosion cell. Due to this corrosion reaction occurs on their surface, aluminium is oxidized into Al3+. The corrosion reaction accelerates deterioration in metal and it produces galvanic, pitting, stress, crevice, intergranular corrosion. Chloride ions decrease internal and external strength of aluminium metal. It is a very important metal so used in different appliances for e.g. road, water, air transports, housing, railways and other fields. Nanocoating and electrospray techniques used to check the corrosion of aluminium metal. For nanocoating and electrospray materials applied tetrahydro-dibenzo[a,d] [7] annulene-5, 11-dihydrazone and MgO. Both materials formed composite barrier and developed a passive surface for Cl- ions. This barrier reduced the corrosion rate of aluminium. Nozzle spray and chemical vapour deposition technique used for coating process. The corrosion rate of metal was determined by gravimetric method. Corrosion potential and current density were calculated by potentiostat. The composite barrier formation was confirmed by activation energy, heat of adsorption, free energy, enthalpy and entropy. These thermal parameters were obtained by Arrhenius equation, Langmuir isotherm and Transition state equation. The adsorption of tetrahydro-dibenzo[a,d] [7] annulene-5,11-dihydrazone and MgO electrospray on aluminium surface was depicted by Langmuir, Frundlich and Temkin isotherm. The results of surface coverage area and coating efficiency were noticed that both materials were mitigated the corrosion rate of aluminium in chloride ions environment

The Effect of Circulation of 3% HCL Solution On the Corrosion Rate of Aluminum

Corrosion is usually called rusting. Corrosion to aluminum is carried out by circulating and non-circulating methods. The specimens were placed in 3% HCl solution, each with 3 specimens in one vessel. There are 9 specimens in 3 vessels. In this study, aluminum was immersed with a circulation of 385 L/hour and 432 L/hour and also without circulation with immersion time for 4 days. The highest corrosion rate was obtained in aluminum soaked in 3% HCl for 4 days with a circulation of 432 L / hour, 0.5215 Mpy. The lowest corrosion rate was obtained for aluminum immersed in 3% HCl for 4 days without circulation, 0.1830 Mpy.

A promising hybrid additive for enhancing the performance of alkaline aluminum-air batteries

The low anode utilization and large capacity loss of aluminum due to the severe self-corrosion in alkaline electrolyte extremely restrict the practical applications of aluminum-air batteries. The vital challenge lies in the issue to slow down the self-corrosion rate without decreasing the discharge performance of aluminum anode. In this work, the application of zinc sulfate (ZnSO4) and sodium alginate (SA) as electrolyte additives to mitigate the corrosion of aluminum is investigated by hydrogen evolution test as well as the electrochemical measurements. The results show that zinc sulfate decreases the corrosion rate of aluminum mainly by restraining the cathodic reaction and exerts positive effect on the improvement of discharge performance for aluminum-air batteries. The hybrid ZnSO4/SA additive exhibits higher inhibition efficiency for the corrosion of aluminum than single ZnSO4 or SA, the adsorbed SA stabilizes zinc layer and improves the protective performance. Moreover, the cell voltage is prominently elevated while the discharge capacity increases from 162.46 to 267.41 mAh cm−2 with the dosage of 10 mM ZnSO4 and 1 g/L SA. A possible model is also proposed to elaborate the influence mechanism of the additive on the self-corrosion behavior and discharge performance of aluminum-air batteries.

Influence of the Supernatant of Trehalose-Lipid Culture Liquid on the Corrosion of 20 Steel and Aluminum in Chloride Solutions

It is shown that the supernatant of trehalose-lipid culture liquid, which is the product of vital activity of R.erythropolis Au-1 bacteria, exerts an anticorrosion influence on 20 steel and aluminum both in a 0.1% NaCl medium and in a model solution of stratal water. Thus, in 0.1% NaCl, within the temperature range 25–50°С, the supernatant of trehalose-lipid culture liquid makes the corrosion rate of 20 steel 6.2–4.3 times lower and the corrosion rate of aluminum 2–3.8 times lower. At the same time, in the model solution, the corrosion rates become 2.9–1.5 times lower for 20 steel and 3.1–3.2 times lower for aluminum. It is shown that the inhibiting properties of the supernatant of trehalose-lipid culture liquid are explained by its retarding action upon both electrode reactions caused by its adsorption on the metal surfaces.

Estimated and Stationary Atmospheric Corrosion Rate of Carbon Steel, Galvanized Steel, Copper and Aluminum in Iran

Atmospheric corrosion of structural metals including aluminum, copper, carbon steel and galvanized steel has been investigated in various areas in Iran based on meteorological data and test coupon mass loss. Using annual average temperature and relative humidity (RH), the time of wetness (TOW, τ) of 51 cities in Iran was obtained in 2012. Coincidentally, sulfur dioxide (SO2) and chloride ion (Cl−) concentrations were measured in these cities; then, according to ISO 9223, the predicted corrosion rate (rcorr) of aluminum, copper, carbon steel and galvanized steel was calculated. Geographical information system (GIS) modeling of TOW, air pollutants (sulfur dioxide and chloride ion) and estimated rcorr were extracted. The mentioned metallic coupons were exposed to the outdoor atmosphere of 15 test sites for up to 12 months to measure the actual corrosion rate of metals. The corrosion products were characterized using scanning electron microscopy and an X-ray diffractometer. The results show that the atmospheric corrosivity of Iran as a developing country is mainly affected by the air temperature, RH and Cl− deposition rate. The atmosphere at shorelines is much more aggressive. Predicting the corrosion loss, the northern coastlines show a more corrosive atmosphere. On the contrary, coupons fixed at the southern coastlines are severely corroded compared with those fixed at the northern shorelines. Chabahar has the most corrosive atmosphere for carbon steel, galvanized steel and copper coupons where their actual corrosion rates (CRs) are 514.68, 10.25 and 11.01 μm/year, respectively. Aluminum coupons presented the best corrosion resistance at all test sites, and their CR were approximately nil. The result shows that models developed by ISO 9223 are not appropriate for predicting the atmospheric corrosion of aluminum, copper, galvanized steel and carbon steel in most areas in Iran.

Corrosion Mitigation of Gray Cast Iron and Aluminum in NaOH Using Water Hyacinth (Eichhornia crassipes) Plant Extract

This research focused on the corrosion behavior of gray cast iron and aluminum in alkaline medium (0.5 M NaOH) with and without inhibitor (water hyacinth Eichhornia crassipes extract) of varying concentrations of 5%, 10%, 15%, 20% and 25%. The corrosion rates of the metal samples were investigated using the weight loss and electrochemical methods alongside the formulation of a dispersant using readily available chemicals to develop a colloidal solution of the extract produced by hot water digestion of the water hyacinth plant leaves. The metallography tests of control samples as well as the most and least corroded samples were carried out using Optical Microscope (OM). The results revealed that the aluminum resulted in minimum corrosion rate of 0.000483 mg/mm2/yr with inhibitor efficiency of 98.93% obtained for sample A5 (25% extract from water hyacinth) while for the gray cast iron, a minimum corrosion rate of -4.4E-05 mg/mm2/yr with inhibitor efficiency of 566.6% obtained for sample C3 (15% extract from water hyacinth). The electrochemical result of aluminum showed increase in corrosion potential from -1.494 VAg/AgCl to -1.482 V Ag/AgCl and that of gray cast iron from -0.5436 VAg/AgCl to -0.2839 VAg/AgCl upon increase in inhibitor concentration. Therefore, the use of water hyacinth (Eichhornia crassipes)extract reduced the corrosion or dissolution rate of gray cast iron and aluminum in (NaOH) sodium hydroxide medium.