The influence of chemistry apart from the pH of buffers on the electrochemical corrosion behaviours of mild steel (MS) and 7004 aluminium alloy (AA) was studied using acetate, citrate, and citrate-phosphate buffers having an identical pH of 4. While the buffers showed marginal to insignificant variations in their anodic and cathodic kinetics on Pt, the cathodic current density for MS and AA in these buffers increased in the order citrate < citrate-phosphate < acetate. As for the anodic current density, it increased in the order: acetate < citrate < citrate-phosphate for MS and citrate < acetate < citrate-phosphate for AA. Such variations were explained based on the direct reduction of the weak acids and the complexing behaviour of the metal ions with the buffer species. The study suggests the importance of considering buffer chemistries while studying the influence of pH on electrochemical corrosion including localized corrosion behaviour of metals.
ZaidBSaidiDBenzaidA. Effects of pH and chloride concentration on pitting corrosion of AA6061 aluminum alloy. Corros Sci. 2008; 50: 1841–1847.
2.
PardoAOteroEMerinoMC. Influence of pH and chloride concentration on the pitting and crevice corrosion behavior of high-alloy stainless steels. Corrosion. 2000; 56: 411–418.
3.
PruittNCSudarshanTSLouthanMr.Influence of pH on the crevice corrosion and stress corrosion cracking behavior of 304 stainless steel. J Mater Eng. 1988; 10: 99–108.
4.
GovindarajanSCragnolinoG.Effect of pH on the intergranular stress corrosion cracking of sensitized AISI 304 stainless steel in high temperature sulfate solutions. J Electrochem Soc. 1987; 134: 2986–2992.
5.
TsaiW-TDuhJ-BYehJ-J. Effect of pH on stress corrosion cracking of 7050-T7451 aluminum alloy in 3.5 wt% NaCl solution. Corrosion. 1990; 46: 444–449.
6.
BogarFDFujiiCT. Solution chemistry in crevices on Fe-Cr binary alloys, AD Rep. No. 778002/ 6GA, US Nat. Tech. Inform. Serv. 1974.
7.
FrankelGS.Pitting corrosion of metals: a review of the critical factors. J Electrochem Soc. 1998; 145: 2186–2198.
8.
Szklarska-SmialowskaZ.Pitting corrosion of aluminum. Corros Sci. 1999; 41: 1743–1767.
9.
CuiJYuanWYuanD. Effect of pH on the passivation of carbon steel by sodium borosilicate controlled release inhibitor in simulated recirculating cooling water. Ind Eng Chem Res. 2017; 56: 7239–7252.
10.
KlapperHSStevensJ.Susceptibility to pitting corrosion of nickel-based alloy 718 exposed to simulated drilling environments. Corrosion. 2014; 70: 899–906.
11.
AbdulsalamMI.Behaviour of crevice corrosion in iron. Corros Sci. 2005; 47: 1336–1351.
12.
ScoppioLBarteriMLealiC.Sulphide stress cracking resistance of superduplex stainless steels in oil and gas field simulated environments. CORROSION 98. San Diego, CA: NACE International; 1998.
13.
VelozMAGonzálezI.Electrochemical study of carbon steel corrosion in buffered acetic acid solutions with chlorides and H2S. Electrochim Acta. 2002; 48: 135–144.
14.
SinghMMGuptaA.Corrosion behavior of mild steel in acetic acid solutions. Corrosion. 2000; 56: 371–379.
15.
KoehlerELEvansS.Pitting and uniform corrosion of aluminum by pH 3.5 citrate buffer solution. J. Electrochem Soc. 1964; 111: 17–21.
16.
MacdonaldDDSmedleySI.An electrochemical impedance analysis of passive films on Nickel (111) in phosphate buffer solutions. Electrochim Acta. 1990; 35: 1949–1956.
17.
BhardwajRCGonzalez-MartinABockrisJO'M.In situ scanning tunneling microscopy studies on passivation of polycrystalline iron in borate buffer. J Electrochem Soc. 1991; 138: 1901–1908.
18.
DanieleSLavagniniIBaldoMA. Steady state voltammetry at microelectrodes for the hydrogen evolution from strong and weak acids under pseudo-first and second order kinetic conditions. J Electroanal Chem. 1996; 404: 105–111.
19.
Gonzalez-PenaOIChapmanTWVongYM. Study of adsorption of citrate on Pt by CV and EQCM. Electrochim Acta. 2008; 53: 5549–5554.
20.
WieckowskiASobkowskiJZelenayP. Adsorption of acetic acid on platinum, gold and rhodium electrodes. Electrochim Acta. 1981; 26: 1111–1119.
21.
SinghSKMukherjeeAK.Kinetics of mild steel corrosion in aqueous acetic acid solutions. J Mater Sci Technol. 2010; 26: 264–269.
22.
BryanJM.The corrosion of aluminium and aluminium alloys by citric acid and citric acid-salt solutions. J Sci Food Agric. 1950; 1: 84–87.
23.
DanieleSLavagniniIBaldoMA. Voltammetry for reduction of hydrogen ions from mixtures of mono- and polyprotic acids at platinum microelectrodes. Anal Chem. 1998; 70: 285–294.
24.
KahyarianABrownBNešićS.Mechanism of cathodic reactions in acetic acid corrosion of iron and mild steel. Corrosion. 2016; 70: 1539–1546.
25.
GarsanyYPletcherDSidorinD. Quantifying the acetate-enhanced corrosion of carbon steel in oilfield brines. Corrosion. 2004; 60: 1155–1167.
26.
RodičPMiloševILekkaM. Study of the synergistic effect of cerium acetate and sodium sulphate on the corrosion inhibition of AA2024-T3. Electrochim Acta. 2019; 308: 337–349.
27.
RodičPMiloševI.The influence of additional salts on corrosion inhibition by cerium(III) acetate in the protection of AA7075-T6 in chloride solution. Corros Sci. 2019; 149: 108–122.
28.
DawsonRMCElliotDCElliotWH. Data for biochemical research. 3rd ed. Oxford: Clarendon Press; 1986; p. 427-429.
29.
ButlerJN.Solubility and pH calculations: The mathematics of the simplest ionic equilibria. Addition-Wesley Publishing Company, Inc; 1964.
30.
MarinovicVDespicAR.Cathodic hydrogen evolution from aqueous solutions of acetic acid. Russ J Electrochem. 2004; 40: 1155–1160.
31.
MarinovicVDespicAR.Hydrogen evolution from solutions of citric acids. J Electroanal Chem. 1997; 431: 127–132.
32.
ApelblatA.Citric acid. Springer International Publishing; 2014.
33.
ShinagawaTGarcia-EsparzaATTakanabeK.Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion. Sci Rep. 2015; 5: 13801.
34.
HsuehK-LGonzalezERSrinivasanS.Electrolyte effects on oxygen reduction kinetics at platinum: a rotating ring-disc electrode analysis. Electrochim Acta. 1983; 28: 691–697.
35.
GanFChinD-T.Determination of diffusivity and solubility of oxygen in phosphoric acid using a transit time on a rotating ring-disc electrode. J Appl Electrochem. 1993; 23: 452–455.
36.
LozarJBachelotBFalgayracG. Diffusivity and solubility measurement of oxygen in water-acetic acid-sodium acetate solutions on a rotating ring disc electrode. Electrochim Acta. 1998; 43: 3293–3296.
37.
FloateSHosseiniMArshadiMr. An in-situ infrared spectroscopic study of the adsorption of citrate on Au(111) electrodes. J Electroanal Chem. 2003; 542: 67–74.
38.
HenryVK, ed. CRC handbook of thermophysical and thermochemical data. Boca Raton, FL: CRC press Inc; 1994.
39.
NordHBech-NielsenG.The anodic dissolution of iron-III. Coverage on iron in the active and passive states in acid carboxylate solutions. Electrochim Acta. 1971; 16: 849–864.
40.
SerugaMHasenayD.Electrochemical and surface properties of aluminium in citric acid solutions. J Appl Electrochem. 2001; 31: 961–967.
41.
MarinovicVDespicAR.Phosphoric acid as a source of hydrogen in cathodic hydrogen evolution. J Serb Chem Soc. 1998; 63: 545–553.
42.
SekineIHayakawaTNegishiT. Analysis for corrosion behavior of mild steels in various hydroxy acid solutions by new methods of surface analyses and electrochemical measurements. J Electrochem Soc. 1990; 137: 3029–3033.
43.
Stability Constants, Supplement No. 1, Special Publication 25. London: The Chemical Society; p. 252 and 254.
44.
PerriDD.338. The stability of iron complexes. Part IV. Ferric complexes with aliphatic acids. J. Chem. Soc. 1959: 1710–1717.
45.
VukosavPMlakarMTomisicV.Revision of iron(III)-citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies. Anal Chim Acta. 2012; 745: 85–91.
46.
ArpPAMeyerWL.Formation constants for selected organo-metal (Al3+, Fe3+)-phosphate complexes. Can J Chem. 1985; 63: 3357–3366.
47.
SherlockJCBrittonSC.Complex formation and corrosion rate for tin in fruit acids. Br Corros J. 1972; 7: 180–183.
48.
KubickiJDBlakeGAApitzSE.Molecular orbital models of aqueous aluminum-acetate complexes. Geochim Cosmochim Acta. 1996; 60: 4897–4911.
49.
MotekaitisRJMartellAE.Complexes of aluminum(III) with hydroxyl carboxylic acids. Inorg Chem. 1984; 23: 18–23.
50.
KatohM.Influence of chelating agent (citric acid) and F− on corrosion of Al. Corros Sci. 1968; 8: 423–431.
