Stability of spontaneous passive films on high strength Mo-containing stainless steels in aqueous solutions

Heakal, F. El-Taib; Ghoneim, A. A.; Fekry, Amany M.

doi:10.1007/s10800-006-9271-3

Cited by 49 publications

(28 citation statements)

References 31 publications

(40 reference statements)

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“…Furthermore, at any sulfate concentration the OCP of alloy II is always more noble than that for pure Ag. The ennobling of potential signifies additional passivation due to thickening and self-healing of the surface oxide film [15,16]. The behavior of alloy II accords with previous report indicating that the presence of a small amount of tin reduces the corrosion ability of Ag-Sn surface [13].…”

Section: Effect Of Concentrationsupporting

confidence: 83%

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

Ameer

Ghoneim

Fekry

2010

Materials & Corrosion

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The corrosion and passivation behavior of four binary xSn-Ag (x ¼ 26, 50, 70, and 96.5 wt%) alloys and their pure metal components was investigated in sodium sulfate solutions using electrochemical techniques. The influence of two different electrolytic parameters, namely, concentration (0.01-1.0 M) and pH (3.0-11.0) were studied while the specimens were potentiodynamically polarized between À1000 and 500 mV versus saturated calomel electrode (SCE). The results showed that the corrosion current density (i corr ) increases with increasing either the tin content in the alloy or the SO 2À 4 ions concentration in the electrolyte. Increasing the pH value of a constant composition sulfate solution was found to improve the corrosion resistance of the tin-richer alloys (x ¼ 50-96.5 wt%), and decreases a little the stability of the silver-rich one (74 wt% Ag). Impedance measurements at the free corrosion potential (E corr ) give good support for these results, where a small addition of tin to silver up to the intermetallic ratio (x ¼ 26 wt%) gives an alloy with better corrosion resistance to the aggressive sulfate medium. In terms of the tin ratio, the order of surface film stability on the tested samples, generally follows the ranking: 26 > 96.5 > 50 > Ag > 70 > Sn. The good corrosion resistance of the tin-rich alloy (x ¼ 96.5 wt%), surpassing those for the pure constituents tin and silver can be attributed to the homogenous phase structure of this eutectic mixture.

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Section: Effect Of Concentrationsupporting

confidence: 83%

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

Ameer

Ghoneim

Fekry

2010

Materials & Corrosion

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“…The increase in the R p values in the presence of different concentrations of PMN, MMN, NBT and MBN indicates reduction in the MS corrosion rate with the formation of adsorbed protective film on the metal-solution interface [47,48]. When the concentration was raised from 200 to 500 ppm, there was a gradual increase in the diameter of each semicircle of the Nyquist plot reflecting the increase in R p values from 27.81 to 163.8, 190.5, 316.8 and 562.0 X cm 2 for PMN, MMN, NBT and MBN, respectively which indicates the adsorption of inhibitor molecules on the metal surface and also increase in stability of inhibitors film adsorbed on the metal surface.…”

Section: Potentiodynamic Polarization Studiesmentioning

confidence: 99%

Corrosion inhibition effect and adsorption behaviour of nicotinamide derivatives on mild steel in hydrochloric acid solution

2014

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Background A new class of nicotinamide derivatives viz., N-((1H-pyrrol-2-yl)methylene)nicotinamide, N-((methyl-(phenyl)amino)methylene)nicotinamide, N-nicotinoylbenzimidothioic acid and N-(4-(methylthio)benzylidene)nicotinamide have been synthesized and their corrosion inhibition effect on mild steel in 0.5 M HCl was investigated by mass loss, Tafel polarization technique and AC impedance measurements. Results The inhibition efficiency of the inhibitors on mild steel in 0.5 M HCl has been studied based on concentration, time interval and temperature. Potentiodynamic polarization studies showed that all the examined inhibitors suppress both anodic and cathodic process and behave as mixed type of corrosion inhibitors. Conclusions The adsorption of all the inhibitors was found to obey Langmuir isotherm model. Electrochemical impedance data revealed that polarization resistance (R P ) increases and double layer capacitance (C dl ) decreases as the concentration of the inhibitors increases. FTIR, EDX and SEM analyses were performed to study the film persistency of the inhibitors.

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“…1, it can be concluded that film growth follows a direct logarithmic law (Eq. 1) for which the formation process is the rate-limiting step [13]:…”

Section: Open Circuit Potentialmentioning

confidence: 99%

“…Thus, at pH 11.8 the E st value lies nearly midway between those for PO 3À 4 and HPO 2À 4 solutions and at pH 4.5 E st was found to be higher than that for H 2 PO À 4 medium, while at pH 9.1 it acquires its highest measured value. This implies that pH, as well as nature of the prevailing anions contribute to the spontaneous passivation of AZ91D alloy through possible incorporation of these anions into the lattice structure of the growing film [16], where they are located within the outer part of the passive film [13].…”

Section: Open Circuit Potentialmentioning

confidence: 99%

“…Theoretically, film capacitance is related to film thickness (d) by the formula: C T = e o e r A/d, where A is the film area, e o and e r are the dielectric constants of vacuum and film, respectively. Although the actual value of e r within the film is difficult to estimate, a change in C T can be used as an indicator for change in the film thickness [13,21,22].…”

Section: Eis Measurementsmentioning

confidence: 99%

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Electrochemical behavior of AZ91D magnesium alloy in phosphate medium—part I. Effect of pH

2008

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The influence of pH on the corrosion behavior of Mg-based AZ91D alloy was investigated in a constant composition phosphate medium using various electrochemical techniques, complemented with surface analysis data. The studied solutions were 0.1 M H 3 PO 4 , NaH 2 PO 4 , Na 2 HPO 4 and Na 3 PO 4 having pH values of 1.8, 4.5, 9.1 and 11.8, respectively. Spontaneous passivation was substantiated from monitoring the continuous positive shift of the open circuit corrosion potential with both immersion time and solution pH. The impedance data indicated more improvement in the insulating properties of the corrosion products formed on the alloy surface with increase in pH. The electrolyte pH plays a determinant influence on surface film properties, as films formed in phosphate solutions with higher pH values are thicker, thus affording better protection for the alloy than those formed in acidic solutions. Good agreement was observed between the results obtained from electrochemical techniques and those from EDX and XRD examinations. The alloy is more susceptible to corrosion in acidic phosphate solutions than in the alkaline ones. Crystalline magnesium (Mg), magnesium hydride (MgH 2 ) and magnesium oxide (MgO) were found to be the main constituents of the surface film after holding for 2 h in the acidic phosphate medium.

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Stability of spontaneous passive films on high strength Mo-containing stainless steels in aqueous solutions

Cited by 49 publications

References 31 publications

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

Corrosion inhibition effect and adsorption behaviour of nicotinamide derivatives on mild steel in hydrochloric acid solution

Electrochemical behavior of AZ91D magnesium alloy in phosphate medium—part I. Effect of pH

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