Susceptibility to Pitting Corrosion of Ti-CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V Alloys for Aeronautical Applications

Titanium alloys are used in different industries like biomedical, aerospace, aeronautic, chemical, and naval. Those industries have high requirements with few damage tolerances. Therefore, they are necessary to use materials that present fatigue, mechanical, and corrosion resistance. Although Ti-alloys are material with high performance, they are exposed to corrosion in marine and industrial environments. This research shows the corrosion behavior of three titanium alloys, specifically Ti CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V. Alloys were exposed on two electrolytes to a 3.5 wt % H2SO4 and NaCl solutions at room temperature using cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN) according to ASTM G61 and ASTM G199 standards. CPP technique was employed to obtain electrochemical parameters as the passivation range (PR), corrosion type, passive layer persistence, corrosion potential (Ecorr), and corrosion rate. EN was analyzed by power spectral density (PSD) in voltage. Results obtained revealed pseudopassivation in CPP and PSD exposed on NaCl for Ti-6Al-2Sn-4Zr-2Mo, indicating instability and corrosion rate lower. However, Ti-6Al-4V presented the highest corrosion rate in both electrolytes. Ti-6Al-2Sn-4Zr-2Mo revealed pseudopassivation in CPP and PSD in NaCl, indicating a passive layer unstable. However, the corrosion rate was lower in both solutions.

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Dissolution of chromium in sulfuric acid

Journal of the Serbian Chemical Society ◽

10.2298/jsc0211777d ◽

2002 ◽

Vol 67 (11) ◽

pp. 777-782 ◽

Cited By ~ 8

Author(s):

Dragutin Drazic ◽

Jovan Popic

Keyword(s):

Corrosion Rate ◽

Room Temperature ◽

Corrosion Potential ◽

Analytical Data ◽

Electrochemical Corrosion ◽

Spectrophotometric Analysis ◽

Weight Loss Method ◽

Loss Method ◽

Anomalous Dissolution

By combining electrochemical corrosion rate measurements and spectrophotometric analysis of the electrolyte it was shown that at room temperature chromium dissolves in deaerated 0.1M Na2SO4 + H2SO4 (pH1) solution as Cr(II) and Cr(III) ions in he ratio Cr(II):Cr(III)?7:1. This process was stable over 4h without any detectable change. The total corrosion rate of chromium calculated from the analytical data is about 12 times higher, than that determined electrochemically by cathodic Tafel line extrapolation to the corrosion potential. This finding was confirmed by applying the weight-loss method for the determination of the corrosion rate. This enormous difference between these experimentally determined corrosion rates can be explained by the rather fast, "anomalous" dissolution process proposed by Kolotyrkin and coworkers (chemical reaction of Cr with H2O molecules) occurring simultaneously with the electrochemical corrosion process.

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Localized Corrosion of 304 Stainless Steel under a NaCl Droplet

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.480-481.443 ◽

2011 ◽

Vol 480-481 ◽

pp. 443-447

Author(s):

Yan Hua Wang ◽

Yuan Yuan Liu

Keyword(s):

Stainless Steel ◽

Corrosion Rate ◽

Corrosion Potential ◽

Corrosion Process ◽

Localized Corrosion ◽

304 Stainless Steel ◽

Galvanic Current ◽

Cooperative Effects ◽

Electrochemical Parameters ◽

Wire Beam Electrode

The distributions of corrosion potential and galvanic current of 304 stainless steel under a NaCl droplet were studied by using the wire beam electrode (WBE). It was found that the distributions of the electrochemical parameters were heterogeneous with isolated anodic and cathodic zones appeared randomly. During the corrosion process, the polarity of some anodes changed with the evolution of time. The localized corrosion rate and heterogeneity increased firstly, and then decreased afterward with the increase of time, which can be attributed to the cooperative effects of the aggressive ions and the corrosion products.

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Experimental and Modeling Studies on the Stress Relaxation Behaviour of Ti-6Al-4V Alloy

10.1115/gtindia2021-75873 ◽

2021 ◽

Author(s):

Kali Prasad ◽

Krishnaswamy Hariharan ◽

Dilip K. Banerjee

Keyword(s):

Stress Relaxation ◽

Titanium Alloys ◽

Room Temperature ◽

Hold Time ◽

High Strength ◽

Uniaxial Tensile ◽

Time Data ◽

Transient Stress ◽

Ti Alloys ◽

Strain And Strain Rate

Abstract The transient mechanical behavior of materials during stress relaxation has evoked interest in manufacturing applications because of the effect of stress relaxation on formability enhancement. However, most of the previous studies have focused on advanced high strength steels and aluminum alloys. Limited transient stress relaxation studies have been conducted on titanium alloys in order to understand the influence of stress relaxation on forming behavior. Titanium alloys are widely used in aerospace components because of their high strength to weight ratios and excellent fatigue strengths. However, room temperature formability of Ti alloys is an important concern, which restricts their widespread use in various applications. To address these challenges, the present study is aimed to understand the role of transient stress relaxation on formability of Ti alloys. Toward this end, stress relaxation of a dual phase titanium alloy (Ti-6Al-4V) has been investigated experimentally. Stress relaxation tests were performed by interrupting uniaxial tensile tests in the uniform deformation regime for a pre-defined strain and hold time after which tests were continued monotonically until fracture. Single step, room temperature stress relaxation experiments were performed systematically to study the effect of hold time, pre-strain, and strain rate on mechanical properties. The stress relaxation phenomenon was found to contribute positively to the ductility improvement. The mechanisms responsible for enhancing the formability are discussed. The experimentally obtained stress vs. time data were analyzed using a advanced constitutive model for stress relaxation available in literature.

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Electrochemical Noise Analysis of the Corrosion of Titanium Alloys in NaCl and H2SO4 Solutions

Metals ◽

10.3390/met11010105 ◽

2021 ◽

Vol 11 (1) ◽

pp. 105

Author(s):

Jesús Manuel Jáquez-Muñoz ◽

Citlalli Gaona-Tiburcio ◽

Jose Cabral-Miramontes ◽

Demetrio Nieves-Mendoza ◽

Erick Maldonado-Bandala ◽

...

Keyword(s):

Titanium Alloys ◽

Electrochemical Noise ◽

Noise Analysis ◽

Passive Layer ◽

Polynomial Method ◽

Nacl Solution ◽

Hilbert Huang Transform ◽

Ti Alloys ◽

Density Analysis ◽

Corrosive Environments

Titanium alloys have been used in aerospace, aeronautic, automotive, biomedical, structural, and other applications because titanium alloys have less density than materials like steel and support higher stress than Al-alloys. However, components made of titanium alloys are exposed to corrosive environments, the most common being industrial and marine atmospheres. This research shows the corrosion behavior of three titanium alloys, specifically Ti-CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V with α, near α, and α + β alloys phases. Alloys were exposed in two electrolytes to a 3.5 wt. % H2SO4 and NaCl solution at room temperature, and their electrochemical behavior was studied by electrochemical noise technique (EN) according to ASTM ASTM-G199 standard. EN signal was filtered by three different methods, and the polynomial method was employed to obtain Rn, kurtosis, skew, and the potential spectral density analysis (PSD). The wavelets method was used, from which energy dispersion plots were obtained. The last method was Hilbert–Huang Transform (HHT), where Hilbert Spectra were analyzed. Results indicated that Rn compared with PSD showed that Ti-6Al-2Sn-4Zr-2Mo presented less dissolution in both electrolytes. Statistical methods showed that the passive layer created on Ti alloys’ surfaces is unstable; this condition is notable for Ti-6Al-2Sn-4Zr-2Mo in NaCl solution.

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Molybdates as Corrosion Inhibitors in the Presence of Chlorides

CORROSION ◽

10.5006/0010-9312-32.7.263 ◽

1976 ◽

Vol 32 (7) ◽

pp. 263-266 ◽

Cited By ~ 48

Author(s):

E. A. LIZLOVS

Keyword(s):

Weight Loss ◽

Corrosion Rate ◽

Potentiodynamic Polarization ◽

Room Temperature ◽

Corrosion Inhibitors ◽

Corrosion Potential ◽

Chloride Content ◽

Passive State ◽

Chloride Sulfate ◽

Polarization Studies

Abstract The effect of the molybdate ion (MoO4=) concentration on the corrosion inhibition of 1010 steel was investigated in aerated chloride/sulfate-containing solutions. The chloride content was 304 ppm Cl−, and the sulfate was 352 ppm SO4=. Weight loss measurements and electrochemical methods were employed for the investigation. The pH was controlled at 8.7. Weight loss measurements indicated that about 165 ppm of molybdate reduced the corrosion rate below 10 mg·dm−2/day at room temperature. At 160 F (71 C), about 50 ppm of molybdate reduced the corrosion rate to 4 to 5 mg·dm−2/day. The potentiodynamic polarization studies and the examination of corrosion potential and immersion time relationship disclosed that the molybdate ion acts as a passivating agent in the presence of oxygen. Passivity was also obtained under potentiodynamic polarization conditions in a nitrogenated solution. No passivation was obtained in the absence of the molybdate ion. For spontaneous passivation, both molybdate and oxygen (oxidizing agent) were needed. Corrosion rates in a passive state according to the polarization curve should be nil.

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The Role of Deformation Twinning on Creep of Titanium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.121 ◽

2007 ◽

Vol 561-565 ◽

pp. 121-126

Author(s):

Sreeramamurthy Ankem ◽

P. Gregory Oberson

Keyword(s):

Titanium Alloys ◽

Speed Of Sound ◽

Critical Stress ◽

National Science Foundation ◽

Room Temperature ◽

Deformation Twinning ◽

Ti Alloys ◽

National Science ◽

Recent Developments

Normally, deformation twinning is a process that occurs at rates approaching the speed of sound in bulk metals once a critical stress has been reached. However, recently it has been shown that twins grow at speeds many orders of magnitude lower than the speed of sound during room temperature creep of titanium alloys. The net result is that this twinning process can contribute to the low-temperature (less than 0.25*Tm) creep behavior of α, α−β, and β−titanium alloys. For example, α-Ti alloys with small grain size do not extensively deform by twinning and hence show little overall creep strain. These recent developments are reviewed in this paper. This work is funded by the National Science Foundation under Grant Number DMR-0517351.

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Electrochemical Corrosion Behaviour of Mg-(Ca,Mn) Sacrificial Anodes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.795.530 ◽

2013 ◽

Vol 795 ◽

pp. 530-534

Author(s):

Shaiful Rizam Shamsudin ◽

Azmi Rahmat ◽

Mahdi Che Isa ◽

Mohd Nazree Derman ◽

Abdul Razak Daud

Keyword(s):

Corrosion Rate ◽

High Performance ◽

Corrosion Behaviour ◽

Electrochemical Corrosion ◽

Inert Atmosphere ◽

Passive Layer ◽

Open Circuit ◽

Standard Samples ◽

Casting Technique ◽

Small Content

The aim of the study is to identify the effect of Ca in Mg-Mn alloy on electrochemical corrosion behavior for the development of high performance sacrificial anode. Mg alloys were fabricated by casting technique under an inert atmosphere. 0.35 ~ 1.11 wt.% of Ca were added as alloying element. The finding shows that the addition of small Ca in Mg-Mn anodes was found not significantly affecting the corrosion rate. However, small content of Ca was as much as necessary improving electronegativity of open circuit potential and modifying anodic polarization in promoting the instabilities of surface passive layer hence results in the further dissolution process between ion and alloy species underneath. No passivation occurs on the standard samples. Pitting profile only occur on Mg-Mn anode that has lower Ca content (0.35 wt. %). An XRD result shows no present of Mg2Ca phase on the as-cast anode containing 1.11 wt. % Ca. As a conclusion, the influence of small content of Ca was profoundly modifying electrochemically behaviour of Mg containing Mn anodes except corrosion rate.

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Direct Observation of the Diffusionless β → β + ω Transformation in Titanium Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100064669 ◽

1971 ◽

Vol 29 ◽

pp. 122-123

Author(s):

N. E. Paton ◽

D. de Fontaine ◽

J. C. Williams

Keyword(s):

Electron Microscope ◽

Titanium Alloys ◽

Direct Observation ◽

Dark Field ◽

X Ray Diffraction ◽

Resistivity Measurements ◽

Selected Area Electron Diffraction ◽

Ti Alloys ◽

Thin Foils ◽

Field Device

The electron microscope has been used to study the diffusionless β → β + ω transformation occurring in certain titanium alloys at low temperatures. Evidence for such a transformation was obtained by Cometto et al by means of x-ray diffraction and resistivity measurements on a Ti-Nb alloy. The present work shows that this type of transformation can occur in several Ti alloys of suitable composition, and some of the details of the transformation are elucidated by means of direct observation in the electron microscope.Thin foils were examined in a Philips EM-300 electron microscope equipped with a uniaxial tilt, liquid nitrogen cooled, cold stage and a high resolution dark field device. Selected area electron diffraction was used to identify the phases present and the ω-phase was imaged in dark field by using a (101)ω reflection. Alloys were water quenched from 950°C, thinned, and mounted between copper grids to minimize temperature gradients in the foil.

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