Corrosion Inhibitor Concentration Research Articles

Study on efficiency of corrosion inhibitors based on derivatives of isothiuronic salts

Metals play a pivotal role in industry; their use constantly grows. It is virtually impossible to find an industrial field without the use of metals and their alloys. However, owing to the quality degradation of metal during the operational process, corrosion appears not only on its surface but also under a coating, which leads to its destruction. To avoid this, corrosion inhibitors are necessary. Organic compounds have been widely used as corrosion inhibitors. Many organic corrosion inhibitors have been developed nowadays. In the literature, organic compounds comprising N, O, S and P heteroatoms are described, which reduce corrosion rate. The organic compounds are adsorbed on the metal surface, forming a thin layer. Adsorption occurs either through electrostatic interaction or, in some cases, the formation of covalent bonds. The work aimed to study isothiuronic salts as corrosion inhibitors to evaluate their protective properties using the polarisation curves method. Objects of research were isothiuronic compounds containing two active centres separated by saturated and unsaturated carbon bonds (structures 1-3). In structures 4-7, one isothiuronic fragment has different propylene substituting groups. It has been previously shown that these compounds can act as effective brightening agents when applying nickel coatings. A model solution with a density of 1.12 g/cm3 was prepared to study the corrosion inhibitors. The corrosion inhibitor concentration was 400 mg/L. Studies have shown that the compounds with two isothiuronic moieties do not always exhibit improved properties for inhibiting metal degradation in a corrosive environment. In particular, they showed worsening of the inhibiting properties for samples made of steel 20 and identical properties for that made of steel 3.

Electrochemical and surface analytical studies of transition metal bipyridine dicarboxylic acid complexes as corrosion inhibitors for a mild steel in HCl solution

The 2,2′-bipyridine-3,3′-dicarboxylic acid (bpda) and its transition metal complexes including Ni(bpda)2, Zn(bpda)2 and Mn(bpda)2, were synthesized and tested as corrosion inhibitors for a carbon steel in 0.5 M HCl solution by electrochemical tests and surface analyses. The electrochemical results indicate that the inhibition efficiencies increase with the concentration of corrosion inhibitors. The complexes exhibit higher inhibition efficiencies compared to the bpda ligand, among which Ni(bpda)2 is the most effective for inhibiting corrosion. The corrosion morphology observation further evidences the superior corrosion inhibition performance of the three complexes. Fourier transform infrared and X-ray photoelectron spectroscopy analyses confirm the spontaneous adsorption of all four inhibitors on the steel surface, and the adsorption analysis suggests a combined physisorption and chemisorption mechanism. Accordingly, the superior corrosion inhibition performance of the three complexes could be attributed to their good adsorption abilities.

Theoretical and surface/electrochemical investigations of walnut fruit green husk extract as effective inhibitor for mild-steel corrosion in 1M HCl electrolyte

The present paper has studied the corrosion inhibition property of Juglone extracted from walnut (Juglans regia L.) green husk for mild steel samples exposed to an acid electrolyte (1 M HCl). Besides, via computer modelings, the attraction forces of the inhibitors/metal surface were explored. The corrosion inhibition efficiency of the organic inhibitor was evaluated using potentiodynamic polarization as well as EIS techniques. In addition, XPS, FT-IR, SEM, AFM, and UV–visible spectroscopy have been used to study the inhibition mechanism of the agricultural waste extract in the corrosive media. Quantum chemical calculations based on DFT theory and molecular dynamic simulations were investigated on the adsorbed Juglone inhibitors. The obtained results indicated that the efficiency of the used inhibitor was enhanced with increasing the concentration of green corrosion inhibitor (GCI) and reached 95% in the presence of 800 ppm after 8 h immersion. Moreover, the average roughness of the exposed metal to the corrosive electrolyte decreased from 68.2 ± 8.3 nm for the blank solution to 3.4 ± 0.3 nm for the solution containing 800 ppm GCI. Furthermore, the Tafel extrapolated polarization results revealed that the extracted GCI functioned as a mixed-type corrosion inhibitor. Finally, the obtained analysis results are supported by theoretical data.

Effect of imidazoline inhibitor on stress corrosion cracking of P110 steel in simulated annulus environments of CO2 injection well

• The SCC of a P110 steel in a simulated annulus environment has been investigated. • Inadequate dose of imidazoline inhibitor will greatly increases SCC susceptibility. • The application of corrosion inhibitor to control SCC should be carefully considered. In this study, the effect of imidazoline inhibitor on the stress corrosion cracking (SCC) behavior of P110 steel in a simulated annulus environment in CO 2 injection wells was investigated by immersion tests on three-point bending specimens, electrochemical measurements, and corrosion morphology analysis. Results show that the addition of imidazoline inhibitor may lead to a high sensitivity of SCC for P110 steel. In the absence of tensile stress, P110 steel gains effective protection when the corrosion inhibitor concentration is less than 1000 mg/L. However, under various tensile loadings, the SCC susceptibility, which in the presence of the inhibitor is higher than that in the absence of the inhibitor, increases with an increase in the concentration of the inhibitor (when the inhibitor concentration is less than 1000 mg/L). The SCC sensitivity starts to reduce if the inhibitor is added continuously; when the inhibitor concentration reaches 2000 mg/L, SCC becomes markedly suppressed. The above phenomenon manifests that the addition of an inhibitor needs careful consideration and the SCC test must be introduced to evaluate the efficiency of the inhibitors; electrochemical analysis and immersion tests of non-SCC samples alone are insufficient to assess the controlling efficiency of inhibitors.

Exploring combined effect of nitrilotriacetic acid and inhibitor on copper surface in alkaline solution: Insights from experiments and molecular dynamics simulation studies

This work aimed to clarify the combined effect of a complexing agent (nitrilotriacetic acid; NTA) and inhibitor (2,2′-{[(methyl-1H-benzotriazol-1-yl)methyl]imino}bisethanol; TT-LYK), which are essential for the development of polishing slurries with excellent performances. Static etch rate (SER) experiments, scanning electron microscopy (SEM), and polishing experiments revealed that NTA is an effective copper complexing agent, and TT-LYK has a better corrosion inhibition effect under static conditions. X-ray photoelectron spectroscopy (XPS) analysis shows that the copper surface contained Cu2O, CuO, and Cu(OH)2 species. Both NTA and TT-LYK could reduce the surface oxidation. The potential polarization curves and electrochemical impedance spectroscopy (EIS) were used to further study the influence of the complexation and corrosion inhibition on the electrochemical properties. Molecular dynamics (MD) simulations clarified the complexation mechanism of NTA and proved that TT-LYK adsorbs on the surface of hydroxylated Cu2O in a tilted mode. The influences of the corrosion inhibitor concentration and liquid flow were systematically evaluated, and the excellent barrier ability of the corrosion inhibitor film to NTA was proven. A combined action mechanism of TT-LYK and NTA was proposed. Finally, response surface methodology (RSM) was used to optimize the slurry developed in this paper to meet the requirements of cobalt barrier polishing.

Efficiency of SS400 steel corrosion bioinhibitor from Moringa leaf (Moringa oleifera L.) extract in NaCl solution medium

Steel was one of a metal mainly used to create things because hard, long-term, and can be generated in large amounts. It was easy getting corrosion, damage to metal material caused by environmental factors. Therefore, it was necessary preventive to reduce the corrosion rate by corrosion inhibitor. A study had been done on the efficiency of steel corrosion SS400 inhibitor from moringa leaf extraction (Moringa oleifera L.) in NaCl 3% solution medium. The objective was to determine soaking time and concentration of corrosion inhibitor from moringa leaf extract to inhibit the corrosion of the steel plate with the highest efficient value. The corrosion examination was conducted with a weight-loss method. Results showed that moringa leaf extract could be used as a corrosion inhibitor for steel plate SS400 in NaCl 3% with soaking time was five days in concentration 2000 ppm was 43.06%.

Determining Critical Micelle Concentration of Organic Corrosion Inhibitors and its Effectiveness in Corrosion Mitigation

Critical micelle concentration (CMC) of a surfactant corrosion inhibitor is considered to be an important property which may indicate its corrosion mitigation efficiency. One of the common methods to determine a CMC is via surface tension measurements of inhibitor solutions. In this work, the validity of surface tension measurement as an indirect technique for the detection of micelle formation is discussed and tested in conjunction with an alternative method—fluorescence spectroscopy, which was used as a technique that more directly detects micelles in a solution. Results show that surface tension measurements of a quaternary ammonium bromide inhibitor solution, that can determine the concentration at which the water/air interface becomes saturated by the inhibitor molecules, does not always correlate with the formation of micelles. In some cases, the formation of micelles occurred in the same concentration range while in others it happened at much higher concentrations, as determined by fluorescence spectroscopy. Moreover, there was no clear correlation between CMC and maximum inhibition of the corrosion rate.

Leakage Failure Analysis of 80SS Tubing in Gas Field

During acidizing process in a gas field, leakage of 80SS anti-sulfur tubing occurred.The main reasons for failure of the tubing have been investigated based on analysis techniques of chemical composition analysis,Optical Microscopy (OM), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) , X-ray Diffraction (XRD) and mechanical test. The results show that composition and mechanical properties of the tubing were all in accordance with the corresponding requirements of API Spec 5CT standards. Furthermore,leakage of tubing from inner wall was caused by combined impacts of acid corrosion, H2S corrosion, low PH value, high temperature and a certain pressure. Meanwhile, Low concentration of corrosion inhibitor was also one of the factors of corrosion perforation.

Evaluation of Palm Kernel Cake Powder (Elaeis guineensis Jacq.) as Corrosion Inhibitor for Carbon Steel in Acidic Media

This work aims to investigate the possible use of the palm kernel cake powder (Elaeis guineensis Jacq.) as corrosion inhibitor for ASTM 1020 carbon steel in acidic media (0.5 mol L−1 HCl). The investigation was carried out using electrochemical impedance spectroscopy (EIS), polarization curves, gravimetric technique and scanning vibrating electrode technique (SVET). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed as chemical and surface characterization techniques, respectively. The results of the EIS and gravimetric tests showed that the substance acts as an effective corrosion inhibitor and inhibition efficiency (IE) increases according with the increase of the corrosion inhibitor concentration in the aggressive medium. The highest IE of 87% was obtained for the highest corrosion inhibitor concentration used (1.77 g/L). The polarization curves revealed a mixed inhibitor. The adsorption of the studied inhibitor on carbon steel surface obeyed Langmuir isotherm. The SVET measurements did not reveal anodic or cathodic activities in the substrate surface in the presence of the inhibitor, revealing that the corrosion inhibitor was able to block both reactions. FTIR analyses identified in the powder the presence of hydroxyl group, aromatic rings, nitrogen and oxygen in such groups as amines and oleaginous acid, which can be responsible for the inhibitory properties of the whole material. SEM analyses showed that the corrosion process was retarded when the inhibitor was added to electrolyte. The results indicate that the powder of palm kernel cake is promising for use as corrosion inhibition purpose for carbon steel in acidic media.

Corrosion Inhibition of Sodium Silicate and Piperazine and Their Synergistic Effect on Carbon Steel in Soft Water Media

The aim of this study is first to investigate piperazine behavior as an inorganic corrosion inhibitor for a ST-14 steel and then to explore synergistical effect of organic (sodium silicate) and inorganic (piperazine) corrosion inhibitors. Due to different corrosion inhibition behavior of these two chemicals, positive results are expected. The corrosion inhibition characteristics of sodium silicate (Na2SiO3) and nitrogen contained organic compound, piperazine (C4H10N2) as corrosion inhibitor for carbon steel was studied using weight loss, Tafel polarization, impedance and some spectrophotometric techniques. Also Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis) and scanning electron microscope (SEM) tests were conducted in order to indicate the formation of a protective film on the surface of steel coupons. The obtained results indicated that the combination of these two inhibitors improve the corrosion behavior about 87 and 76% in accordance with potentiodynamic polarization tests and electrochemical impedance spectrometry, respectively. The corrosion inhibition efficiency has been increased using an optimum combination including 2 ppm piperazine (PIP) and 10–15 ppm sodium silicate. It should be noted that the corrosion inhibition action has been employed using remarkably low concentration of corrosion inhibitors. From the interaction between corrosion inhibitors molecules and iron oxide layer, it can be concluded that the physical adsorption has more effect compared to chemical adsorption in the film formation process for both sodium silicate and PIP inhibitors. It is proposed at least two mechanisms for synergism.

Corrosion Inhibition Performance of Composite Inhibitors for Carbon Steel in Simulated Seawater

Liu, F., 2019. Corrosion inhibition performance of composite inhibitors for carbon steel in simulated seawater. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 397–403. Coconut Creek (Florida), ISSN 0749-0208.In this paper, sodium molybdate, sodium tungstate and sodium citrate were selected to compose a series of corrosion inhibitor solutions in different proportions. Their corrosion inhibition effects on standard Q235 carbon steel in simulated seawater were determined by static weightlessness method, polarization curve method and scanning tunneling microscopy (STM), and the corrosion inhibitor formula having better synergistic corrosion inhibition effect with molybdate was determined through experiments. The results show that the concentration of tungstate inhibitor was too high, but the inhibition rate was very low when tungstate and molybdate are combined. When sodium citrate and molybdate were combined and tungstate was added, the corrosion inhibition rate of the composite inhibitor increased obviously, but increased first and then decreased, indicating that there was an optimum ratio between sodium tungstate and sodium citrate, which made the inhibitor have a good synergistic effect. At the same time, it was found that: (1) sodium tungstate is an anodic corrosion inhibitor which mainly inhibits the anodic reaction; (2) when the concentration of composite corrosion inhibitor is more than 300 mg/L, it can protect Q235 carbon steel well, and the lower the temperature of sea water is, the better the protection effect is.

Analysis of the process of corrosion destruction of settling tanks for preparation of high-viscosity oil to transport through main oil pipelines

Most of accidents and failures of vertical steel tanks are related to metal corrosion of their shells and equipment. The choice of optimal corrosion protection to extend the life of such tanks is impossible without an understanding of the mechanisms of its origin and development, as well as the degree of influence of operational factors on these mechanisms.Of particular interest is the study of corrosion processes taking place in tanks to prepare for the transport of high-viscosity oils operating in the specific conditions of the Far North. The complex effect of factors such as temperature, total salt content of bottom water, the concentration of corrosion inhibitors, demulsifiers, and mechanical impurities on the rate of corrosion processes is not fully understood to date.This article analyzes the process of corrosion destruction of settling tanks for the preparation of high-viscosity oil to transport through main oil pipelines using the example of the RVS-5000 of the park of input tanks of the Yareganeft oil and gas department. Analysis of operating conditions made it possible to identify factors affecting corrosion processes and to identify potentially the most dangerous zones of contact between media entering the reservoir and the shell metal, the bottom and roof of the tank. The study have showed that the greatest interest is the study of the effect of the presence of mechanical impurities in the fluid supplied to the settling tank on the intensity of corrosion processes on the internal surfaces of the tank in potentially dangerous areas.

Effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid solution

In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A 3 steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A 3 steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that Δ H , Δ S , and E a increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process.

Experimental Investigation of a New Derived Oleochemical Corrosion Inhibitor

Most of the corrosion inhibitors that are used in industry contain chemicals that are harmful to health and environment. Corrosion inhibitors derived from green sources are, therefore, believed to be a good option for replacing the chemical corrosion inhibitors. In this work, a green oleochemical corrosion inhibitor derived from Jatropha Curcas is introduced. The paper discusses the methodology of deriving the corrosion inhibitor as well as the experimental test conducted for evaluating its corrosion inhibition efficiency. The new oleochemical corrosion inhibitor was derived via two reactions. Jatropha oil was firstly saponified with sodium hydroxide to yield gras acid and glycerol, which was then esterified with boron fluoride in presence of excess methanol to produce the oil methyl esters, which is used as oleo-chemical corrosion inhibitor. To evaluate the oleo-chemical corrosion inhibitor, the corrosion rate of mild steel in NaCl corrosive medium with CO2 is tested at static condition and two dynamic conditions, namely 500 and 1500 rpm. This is to simulate the transitional and turbulent flow in a pipeline. At each dynamic condition, the proposed corrosion inhibitor was tested at concentration dosages of 0, 50, 100, and 150 ppm. The experiments results revealed a good performance of the new oleochemical corrosion inhibitor. The inhibition efficiency was found to be highly affected by the concentration of corrosion inhibitor. Total corrosion inhibition of the mild steel was noticed by using 150 ppm at dynamic condition of 500 rpm.

Improved Corrosion Resistance of Steel in Ethanol Fuel Blend by Titania Nanoparticles and Aganonerion polymorphum Leaf Extract.

A porous and low-density protective film on a steel surface in the corrosive environment can undergo deterioration even in the presence of organic inhibitors due to infiltration of aggressive ions into the pinholes and/or pores. This phenomenon is related to the localized corrosion that takes place even in the presence of an optimal concentration of organic corrosion inhibitors in the given medium. To overcome this issue, we have designed an organic protective film on a steel surface with the help of titania nanoparticles (TNPs) combined with an organic corrosion inhibitor derived from Aganonerion polymorphum leaf extract (APLE), all to be studied in a simulated ethanol fuel blend (SEFB). The TNPs with varied diameters and concentrations have been studied for examining their effect on the inhibition capacity of 1000 ppm APLE on the steel surface in SEFB medium using electrochemical and surface analysis techniques. Enhanced corrosion inhibition of the surficial film was observed in the presence of both the APLE inhibitor and small amounts of TNPs. A direct agreement was observed between the experimental and molecular dynamics theoretical investigations showcasing high binding energy between inhibitor molecules and steel substrates, resulting in a much higher adhesion of the protective film, good thermal stability of the adsorbent film, and electron abundance for the supply of steel substrate of inhibitor species.

Effect of Imidazoline Corrosion Inhibitors on Erosion/Corrosion Processes - an Electrochemical Investigation

Erosion-corrosion is a concern for oil and gas pipelines [1]–[3]. The simultaneous influence of fluid parameters such as velocity, turbulence, fluid regime and the characteristics of the corrosion scales formed on the pipe surface can accelerate erosion-corrosion inside oil and gas pipelines [4]. Corrosion inhibitors, made of imidazoline derivatives, are widely used in oil industry to prevent internal corrosion of pipelines. In this work, the influence of an imidazoline corrosion inhibitor on erosion-corrosion rates, in flowing fluid condition, is electrochemically investigated. The test electrolyte is synthesized to simulate condition of a multiphase gas pipeline. Electrochemical Impedance Spectroscopy (EIS) was used to measure the corrosion rate in presence of varying concentration of corrosion inhibitors. A cylindrical working electrode with a rotational speed of 1200 (rpm) was employed to simulate the dynamic behavior of the flowing fluid inside wet gas pipelines. The results revealed that corrosion inhibitor films could be readily removed from the steel surface by the erosional behavior of the flowing fluid if the adhesion factor of the surface films are not sufficient. This would expose the bare metal to the corrosive medium. The consequence of such phenomena is the lifespan reduction of pipelines and thus occurrence of immature erosion-corrosion failures. This study demonstrated that the adhesion force of the corrosion inhibitor films are directly related to the thickness of the formed film on the pipe surface and the shear stress generated by flow at the steel surface.

Effect of operating parameters and corrosion inhibitors on foaming behavior of aqueous methyldiethanolamine solutions

Corrosion inhibitors are one of the main causes of amine foaming in gas sweetening units. A detailed understanding of amine foaming behavior in the presence of corrosion inhibitors is of great importance if the foaming is to be minimized. In this work, a comparative study was carried out to investigate the foaming tendency and bubbles characteristics of aqueous methyldiethanolamine (MDEA) in the presence of fatty acid-based (Bis(2-Hydroxyehyl)cocoalkylamine; BHCL) and hydrocarbon-based (HCB) corrosion inhibitors. The effect of different operating parameters such as nitrogen flow rate, corrosion inhibitor concentration, foaming time, solution temperature and pore size of the gas diffuser were studied using foam scan instrument. The results showed that on increasing the foaming time, solution temperature and corrosion inhibitor concentrations, the foaming tendency increased. For BHCL, the foam height tends to decrease with a high flow rate and a small pore size of the gas diffuser. Nevertheless, the opposite trend was observed in the presence of the HCB corrosion inhibitor. Depending upon the type of corrosion inhibitors, careful optimization of the operating conditions showed a high potential to minimize amine foaming.

Development of new corrosion inhibitor tested on mild steel supported by electrochemical study

Abstract Mild steel is a metal which is commonly used in industrials and manufacturing of equipment for most industries round the world. It is cheaper cost compared with the other metals and its durable, hard and easy-to-wear physical properties make it a major choice in the manufacture of equipment parts. The main problem through the uses of mild steel in industry is its resistance against corrosion, especially in acidic solutions. This case led to raise the cost of maintenance of equipment that used mild steel and as a result increased costs for the company. Organic corrosive inhibitors that also act as green chemicals, 4-hydroxybenzylideneaminomethyl-5-ethyl-1,3,4-thiadiazol have been synthesized. This inhibitor is tested as corrosion inhibitor on a mild steel sample MS in 1 M hydrochloric acid solution (HCl) using electrochemical measurements test includes PD (Potentiodynamic), EIS (Electrochemical impedance spectroscopy), OCP (Open circuit potential) and EFM (electrochemical frequency modulation). The obtained results indicate that 4-hydroxybenzylideneaminomethyl-5-ethyl-1,3,4-thiadiazol acts as a good corrosion inhibitor for mild steel sample in HCl solution with efficiency above 90%. Changes in the impedance parameters postulated adsorption on the mild steel specimens' surfaces of, which it going to the formation of protective coating layer. It also shows that 4-hydroxybenzylideneaminomethyl-5-ethyl-1,3,4-thiadiazol corrosion inhibitors are effective in helping to reduce and slow down the corrosion process that occurs on mild steel surface in hydrochloric acid solution. Increase of corrosion inhibitor concentration provides a protective layer of mild steel. However, this protective layer becomes weak when the temperature of the solution increases.

Experimental and simulation study of atomization concentration of corrosion inhibitor in a gas pipe

The aim of present study is to investigate the atomization distribution of corrosion inhibitor in the gas pipe via experiments and numerical simulations. The apparatus was set up to study the atomization parameters and concentration. A discrete phase model was applied to study the droplets distribution. The results reveal that the droplets size and atomized angle are closely related to the injection pressure. A higher pressure can contribute a greater atomization field. With the effect of gas flow, the inhibitor droplets would disperse in the pipe and adhere to the inner wall. But the top of pipe is easily absent from the inhibitor film. A modified Longwell diffusion model is developed with the consideration of gravity settling and relaxation theory, with an average experimental deviation of 12.86% or less.

A Novel Organic Conversion Coating based on N-Benzoyl-N-Phenylhydroxylamine Chemistry for the Corrosion Protection of AA2024-T3

This work demonstrates a novel organic conversion coating treatment on an AA2024-T3 substrate. The process is based on simple immersion in aqueous solutions containing an organic molecule, N-Benzoyl-N-phenylhydroxylamine (BPHA), after a hydrothermal oxide has been formed on the alloy surface. Potentiodynamic polarization results indicate that BPHA conversion coating outperforms coatings formed in the same concentration of other corrosion inhibitors, including NaVO3, Na2SiO3, CeCl3, and benzotriazole. BPHA coating also displays strong and persistent corrosion inhibition under ASTM B117 salt spray exposure conditions and static immersion testing. The cross-section of BPHA-coated substrate is prepared by focus ion beam-scanning (FIB), and analyzed by high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) coupled with energy dispersive spectroscopy (EDS), which show a thick surface film with a three-layer structure. Raman spectroscopy and XPS are used to examine the surface chemistry of BPHA-coated samples, both of which suggest the formation of a BPHA surface film, possibly stabilized by the keto-to-iminol conversion that made the BPHA molecule strongly nucleophilic. The formation of BPHA-metal oxide complex seems to be closely related to the excellent corrosion resistance of BPHA coating.