J. L. Polo

Influence of molybdenum on passivation of polarised stainless steels in a chloride environment

Abstract Polarised specimens of AISI 304L and 316L stainless steels (SS) were studied using X-ray photoelectron spectroscopy in conjunction with Ar+-ion sputtering. A 5% NaCl test solution was used at room temperature. The polarised passive films formed consist mainly of chromium oxide and hydroxide and a small proportion of iron oxides. The composition of the films depend strongly on the potential. Chloride and molybdenum ions appear when the AISI 316L SS alloy is polarised at a potential close to pitting potential.

A study on the stability of AISI 316L stainless steel pitting corrosion through its transfer function

Abstract Impedance measurements were made on an electrochemically polarized AISI 316L stainless steel in a 5% NaCl solution at room temperature. Limited information about this electrochemical method is available in the literature. Three polarization sweep rates, 0.10, 0.30 and 0.40 mVxa0s−1 were tested. Nyquist plots at the pitting potential regions show three capacitive loops. A deconvolution method combined with a complex non-linear least squares program was used to determine the individual components of the equivalent circuit and transfer functions. Negative capacitance and resistances were obtained. The impedance data do not satisfy Kramers–Kronig transforms. It is clear that stability conditions are not met for electrode processes indicating surface relaxation.

Substitutional inhibition mechanism of mild steel hydrochloric acid corrosion by hexylamine and dodecylamine

Hexylamine and dodecylamine were investigated as inhibitors of mild steel hydrochloric acid corrosion, in concentrations from 1 × 10−6 to 1.0 M, at a temperature of 298 K. For a given inhibitor concentration, dodecylamine showed higher effectiveness than hexylamine. The inhibitor mechanism was treated as a substitutional adsorption process according to Flory–Huggins (FH), Dhar–Flory–Huggins (DFH) and Bockris–Swinkels (BS) isotherms. The best approach was obtained using FH and DFH isotherms, with one molecule of inhibitor replacing three molecules of water. A structural parameter, the projected molecular area of these two inhibitors, was calculated to elucidate inhibitor orientation in the adsorption process.

Characterization of copper corrosion products originated in simulated uterine fluids and on packaged intrauterine devices

This paper studies the characterization of corrosion products originated after 1 and 12 weeks immersion of copper specimens in simulated uterine fluids at pH 6.3 and 8.0 and at 37 °C temperature. The experimental techniques used were X-ray photo-electron spectroscopy, scanning electron microscopy, and energy dispersive X-ray. The compounds found were calcite (CaCO3), calcium phosphate, cuprite (Cu2O) and copper hydroxide (Cu(OH)2). The morphology of corrosion products was a non-uniform, layer showing some paths through which copper ions can be released. In parallel, corrosion products formed on packaged, unused copper-containing intrauterine devices (IUD) were analyzed. Cuprite (Cu2O) and chalcocite (Cu2S) were the main species identified.

Copper Corrosion Mechanism in the Presence of Formic Acid Vapor for Short Exposure Times

The rate of copper corrosion originated by the action of formic acid vapors at 100% relative humidity was studied. Five formic vapor concentration levels (10, 50, 100, 200, and 300 ppm) were used. A copper corrosion rate of up to 1,300 mg/m{sup 2} d was measured for a period of 21 days using a gravimetric method. The patina layers were characterized using cathodic reduction, X-ray powder diffraction. Fourier transform infrared spectrometry, and scanning electron microscopy techniques. Some of the components identified in the corrosion-product layers were cuprite (Cu{sub 2}O), cupric hydroxide hydrate [Cu(OH){sub 2}{sm_bullet}H{sub 2}O], and copper formate hydrate [Cu(HCOO){sub 2}{sm_bullet}4H{sub 2}O]. The latter was formed by both cupric hydroxide and formic acid-cuprous ion complex mechanisms.

Tributylamine as corrosion inhibitor for mild steel in hydrochloric acid

The corrosion inhibition of mild steel in 2 M hydrochloric acid solution by tributylamine has been investigated using the impedance technique. Tributylamine was studied in concentrations from 5 × 10−4 M to 1 M at a temperature of 298 K. The inhibitor mechanism was treated as a substitutional adsorption process according to Flory-Huggins, Dhar-Flory-Huggins and Bockris-Swinkels isotherms. The best approach was obtained using the latter. A structural parameter, the projected molecular area of tributylamine, was calculated to elucidate inhibitor orientation in the adsorption process.

Early corrosion failure of copper tubing used in air-conditioning units

This paper analyses the causes of the early corrosion failure of phosphorus deoxidized copper tubes which formed part of an air-conditioning unit. The failure of the tubes occurred after 2–3 months service time. X-ray photo-electron spectroscopy (XPS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques were used. Corrosion tests were also performed at the laboratory using three types of uncorroded copper tubes, 40, 80 and 100% relative humidities, 20 and 40°C temperature, and two commercial lubricant oils. Organic acids, chloride and sulphur were found as sources of corrosion failure. n n n nFruhe Korrosionsausfalle von Kupferrohren aus Klimaanlagen n n n nIn dieser Arbeit werden die Ursachen des fruhzeitigen Korrosionsausfalles von mit Phosphor desoxidierten Kupferrohren untersucht, die Bestandteile einer Klimaanlageneinheit waren. Der Ausfall von Rohren geschah nach 2 bis 3 Monaten Betriebszeit. Es wurden fotoelektronische Spektroskopie- (XPS), Auger-Elektronen Spektroskopie- (AES), Rasterelektronenmikroskopie-(SEM) und energiedispersive Rontgenstrahl-Techniken (EDX) benutzt. Korrosionsversuche wurden auch im Labor durchgefuhrt, wobei drei Arten von rostfreien Kupferrohren bei 40, 80, und 100%iger relativer Luftfeuchtigkeit und Temperaturen von 20 und 40°C und mit zwei handelsublichen Schmierolen gepruft wurden. Organische Sauren, Chloride und Schwefel wurden als Ursachen fur die Korrosionsausfalle gefunden.

Localised corrosion of highly alloyed stainless steels in an ammonium chloride and diethylamine chloride aqueous solution

This paper studies the pitting corrosion of highly alloyed stainless steels (SS) immersed in an ammonium chloride and diethylamine chloride aqueous solution at temperatures of 25, 40, 60 and 80°C. Four materials were tested: UNS S 31726 SS, UNS S 31254 SS, UNS S 32550 SS and titanium, for comparative purposes. Gravimetric, after immersion up to 103 days, polarisation curves, impedance, SEM, EDX and optical microscopy were the techniques used. UNS S 31726 SS shows the lowest corrosion resistance. UNS S 31254 and UNS S 32550 SSs show similar behaviour. Titanium presents impedance data three orders higher than the other SS materials. The SS materials present a pseudoinductive behaviour on impedance data, associated with an adsorption process of the amine compound which decreases as the temperature increases. n n n nLokale Korrosion hochlegierter nichtrostender Stahle in wassriger Losung von Ammoniumchlorid und Diathylamin n n n nIn der vorliegenden Arbeit wird die lokale Korrosion hochlegierter nichtrostender Stahle in wassriger Losung von Ammoniumchlorid und Diathylamin bei Temperaturen von 25, 40, 60 und 80°C untersucht. Die Untersuchung erstreckte sich auf vier Materialsorten: UNS S 31726, UNS S 31254, UNS S 32550 und Titan. Die zur Untersuchung eingesetzten Verfahren waren Gravimetrie mit Tauchversuchen und einer Dauer bis zu 103 Tagen, Polarisationskurven, Impedanz, REM und EDX. Der nichtrostende Stahl UNS S 31726 zeigte die geringste Korrosionsbestandigkeit. Die nichtrostenden Stahle UNS S 31254 und UNS S 32550 zeigten ahnliches Verhalten. Mit Titan werden fur die Impedanz um drei Grosenordnungen hohere Werte als bei den untersuchten nichtrostenden Stahlen erhalten. Die Werte fur die Impedanz der nichtrostenden Stahle zeigen ein pseudo-induktives Verhalten, das mit steigender Temperatur abnimmt.

Adsorption of Benzotriazole on Copper Electrode Surfaces in Citric Acid Media

Abstract The corrosion inhibition of copper in 0.001 M to 1.0 M citric acid (C6H8O7) solution by benzotriazole (BTA, C6H5N3) has been investigated using gravimetric measurements. BTA was tested in ...

Trifenylmethane Compounds as Copper Corrosion Inhibitors in Hydrochloric Acid Solution

Abstract Fuchsin basic (FB) and fuchsin acid (FA) were tested as new corrosion inhibitors for copper in 0.001, 0.005, and 0.01 M hydrochloric acid (HCl) solutions. Benzotriazole (BTA) was also tested for comparative purposes. Twelve FB, FA, and BTA concentrations, from 1 × 10−5 M to 1 × 10−1 M, were added to the acid solution at four temperatures ranging from 298 K to 328 K. Gravimetric measurements were performed after 3 h experimentation. The order of inhibition efficiency was FB ∼ BTA > FA. The Frumkin isotherm gave the best fit to the experimental results. The projected molecular area was used to elucidate inhibitor orientation in the adsorption process.