Editorial

3 pages, 200 KiB

Open AccessEditorial

Corrosion and Protection in Aeronautical Alloys

by Facundo Almeraya-Calderón and Jose Chacon-Nava

Metals 2023, 13(6), 1077; https://doi.org/10.3390/met13061077 - 06 Jun 2023

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Corrosion in the aircraft industry continues to be a major problem that directly affects safety, costs, and aircraft availability [...] Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

Research

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20 pages, 52523 KiB

Open AccessArticle

Susceptibility of Dissimilar IN600 Welded Joints to Stress Corrosion Cracking Using Slow Strain Rate Test in Sodium Electrolytes

by Heriberto Granados-Becerra, Víctor H. López-Morelos, Antonio Contreras, Francisco Fernando Curiel-López, Rafael García-Hernández, Jorge Antonio González-Sánchez and Eduardo Cortés

Metals 2022, 12(7), 1112; https://doi.org/10.3390/met12071112 - 28 Jun 2022

Cited by 2 | Viewed by 1310

Abstract

The stress corrosion cracking (SCC) behavior of aged plates of Inconel 600 welded to Inconel 600 plates in the as-received condition was studied using the slow strain rate test (SSRT) in two sodium containing electrolytes at 25 and 80 °C. The aged plate [...] Read more.

The stress corrosion cracking (SCC) behavior of aged plates of Inconel 600 welded to Inconel 600 plates in the as-received condition was studied using the slow strain rate test (SSRT) in two sodium containing electrolytes at 25 and 80 °C. The aged plate was used to simulate damage by the operation service. Electrochemical noise (EN) was used to monitor the SCC. The plates were gas metal arc welded (GMAW) employing ERNiCrMo-3 and ER310 filler wires along with 95% Ar + 3% N₂ + 2% O₂ and 97% Ar + 3% N₂ as the shielding gas, respectively. The microstructure of the welded joints was characterized using optical and scanning electron microscopy. The results of the SCC revealed that when sodium thiosulfate was used, the loss in plasticity was higher in the NiCrMo-3 joint with around a 20 percent decrease. Conversely, in the 310 welds, the loss in plasticity was higher in the sodium hydroxide, which diminished by 12 percent. A few secondary microcracks were observed in the transversal section in specimens of both welds. The results of the EN showed an increase in the potential and current when the sample reached the tensile strength and then decreased when the neck was formed; these changes indicate that some events occurred during the SSRT. The EN data showed two types of corrosion: general corrosion for NiCrMo-3 and mixed corrosion for the 310 welded joint in both environments. Electrochemical polarization was also employed to understand the mechanism of SCC. Full article

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16 pages, 6288 KiB

Open AccessArticle

Corrosion Behavior of Passivated Martensitic and Semi-Austenitic Precipitation Hardening Stainless Steel

by Facundo Almeraya-Calderón, Oliver Samaniego-Gámez, Erick Maldonado-Bandala, Demetrio Nieves-Mendoza, Javier Olguín-Coca, Jesús Manuel Jáquez-Muñoz, José Cabral-Miramontes, Juan Pablo Flores-De los Rios, Raul German Bautista-Margulis and Citlalli Gaona-Tiburcio

Metals 2022, 12(6), 1033; https://doi.org/10.3390/met12061033 - 17 Jun 2022

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Abstract

This research aimed to conduct a passive layer state study on martensitic and semi-austenitic precipitation hardening stainless steels (PHSS) passivated in citric acid and nitric acid baths at 49 and 70 °C for 50 and 75 min and subsequently exposed in 5 wt.% [...] Read more.

This research aimed to conduct a passive layer state study on martensitic and semi-austenitic precipitation hardening stainless steels (PHSS) passivated in citric acid and nitric acid baths at 49 and 70 °C for 50 and 75 min and subsequently exposed in 5 wt.% NaCl and 1 wt.% H₂SO₄ solutions. Corrosion behavior of the passivated material was observed by using potentiodynamic polarization (PP) according to the ASTM G5-11 standard. The microstructural analysis was performed by optical microscopy and scanning electron microscopy (SEM), while the passivated layer was characterized by X-ray photoelectron spectroscopy (XPS). The results indicated that the semi-austenitic-NA-50 min-70 °C sample showed the best corrosion resistance behavior in both solutions. The XPS characterization confirmed that the martensitic and semi-austenitic surface film presented a mixture of chemical compounds, such as Cr₂O₃ and Fe(OH)O, respectively. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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17 pages, 4724 KiB

Open AccessFeature PaperArticle

Corrosion Behavior of Passivated CUSTOM450 and AM350 Stainless Steels for Aeronautical Applications

by Oliver Samaniego-Gámez, Facundo Almeraya-Calderón, José Chacón-Nava, Erick Maldonado-Bandala, Demetrio Nieves-Mendoza, Juan Pablo Flores-De los Rios, Jesús Manuel Jáquez-Muñoz, Anabel D. Delgado and Citlalli Gaona-Tiburcio

Metals 2022, 12(4), 666; https://doi.org/10.3390/met12040666 - 13 Apr 2022

Cited by 12 | Viewed by 2336

Abstract

Custom 450 stainless steel and AM 350 stainless steel are both precipitation hardening stainless steels, which are widely used in a variety of aerospace applications. The former steel exhibits very good corrosion resistance with moderate strength, whereas the latter is used for applications [...] Read more.

Custom 450 stainless steel and AM 350 stainless steel are both precipitation hardening stainless steels, which are widely used in a variety of aerospace applications. The former steel exhibits very good corrosion resistance with moderate strength, whereas the latter is used for applications requiring high strength along with corrosion resistance. In this study, the corrosion behavior of CUSTOM 450 and AM 350 stainless steels passivated in (a) citric acid and (b) nitric acid solutions for 50 and 75 min at 49 and 70 °C, and subsequently exposed in 5 wt. % NaCl and 1 wt. % H₂SO₄ solutions are investigated. Two electrochemical techniques were used: electrochemical noise (EN) and electrochemical impedance spectroscopy (EIS) according to ASTM G199-09 and ASTM G106-13, respectively. The results indicated that passivation in nitric acid made the surface prone to localized corrosion. Statistical and PSD values showed a tendency toward pitting corrosion. On the whole, passivated CUSTOM 450 stainless steel showed the best corrosion behavior in both, NaCl and H₂SO₄ test solutions. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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18 pages, 47235 KiB

Open AccessArticle

Citric Acid as an Alternative to Sulfuric Acid for the Hard-Anodizing of AA6061

by José Cabral-Miramontes, Facundo Almeraya-Calderón, Francisco Estupinán López, María Lara Banda, Javier Olguín-Coca, Luis Daimir López-León, Ivan Castañeda-Robles, Miguel Ángel Esneider Alcalá, Patricia Zambrano-Robledo and Citlalli Gaona-Tiburcio

Metals 2021, 11(11), 1838; https://doi.org/10.3390/met11111838 - 16 Nov 2021

Cited by 7 | Viewed by 4242

Abstract

Hard-anodized is a widely used method in the aeronautical sector to improve aluminum alloys abrasion and corrosion resistance. Aim of this work was to characterize the mechanical properties and resistance hard-anodized aluminum 6061 in citric acid solution as a replacement sulfuric acid solution [...] Read more.

Hard-anodized is a widely used method in the aeronautical sector to improve aluminum alloys abrasion and corrosion resistance. Aim of this work was to characterize the mechanical properties and resistance hard-anodized aluminum 6061 in citric acid solution as a replacement sulfuric acid solution were investigated. Aluminum alloy 6061 was used as the base material to produce the hard anodizing; this process was carried out in a citric and sulfuric acid solution, applying current densities 3 and 4.5 A/cm² and subsequently exposed to 3.5 wt. % NaCl solution. Microstructure and mechanical properties of the anodizing material were characterized by scanning electron microscopy (SEM) and Vickers microhardness (HV). Corrosion behavior of the hard-anodized material it was carried out with electrochemical techniques as cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) respectively. Results obtained indicated that all samples anodized in citric acid solution showed negative hysteresis and lower corrosion current density (1 × 10⁻¹⁰ A/cm²), indicating generalized corrosion on the material surface. EIS results show that anodizing in citric acid solution and a current density of 4.5 A/dm² provides better corrosion protection than a sulfuric acid solution. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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18 pages, 4477 KiB

Open AccessFeature PaperArticle

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

by Jesus Jaquez-Muñoz, Citlalli Gaona-Tiburcio, Alejandro Lira-Martinez, Patricia Zambrano-Robledo, Erick Maldonado-Bandala, Oliver Samaniego-Gamez, Demetrio Nieves-Mendoza, Javier Olguin-Coca, Francisco Estupiñan-Lopez and Facundo Almeraya-Calderon

Metals 2021, 11(7), 1002; https://doi.org/10.3390/met11071002 - 23 Jun 2021

Cited by 24 | Viewed by 3371

Abstract

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 [...] Read more.

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 (E_corr), 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. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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18 pages, 5523 KiB

Open AccessFeature PaperArticle

Corrosion Behavior of Extruded AM60-AlN Metal Matrix Nanocomposite and AM60 Alloy Exposed to Simulated Acid Rain Environment

by Luis Chávez, Lucien Veleva, Sebastián Feliu, Jr., Danai Giannopoulou and Hajo Dieringa

Metals 2021, 11(6), 990; https://doi.org/10.3390/met11060990 - 21 Jun 2021

Cited by 3 | Viewed by 2380

Abstract

The present work compared the initial stages of corrosion process development on the AM60-AlN metal matrix nanocomposite surface and on AM60, during their exposure for 30 days to simulated acid rain solution (SAR). The AlN nanoparticles were observed as “attached” to those of [...] Read more.

The present work compared the initial stages of corrosion process development on the AM60-AlN metal matrix nanocomposite surface and on AM60, during their exposure for 30 days to simulated acid rain solution (SAR). The AlN nanoparticles were observed as “attached” to those of Mn-rich AlMn intermetallic particles, forming clusters. The introduction of 1.0 wt.% AlN (≈ 80 nm) in the AM60 alloy carried a slight grain refinement and favored the formation of a denser and more protective corrosion layer, suggested by the electrochemical impedance spectroscopy (EIS) values of higher charge transfer resistance (R2) and capacitance, characteristic of the double layer in the presence of corrosion products, and also suggested by Rn (EN) values, compared to those of the AM60 alloy. Thus, the concentration of the released Mg-ions from the composite surface was lower. Due to the increase in time of the SAR solution pH, Al de-alloying may occur, as well as Al(OH)₃ formation, as confirmed by XPS analysis. Due to the presence of Cl-ions in SAR solution, localized corrosion was observed, suggested as fractional Gaussian noise of a stationary and persistent process in time, according to the PSD of the corrosion current fluctuations (EN). Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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17 pages, 5095 KiB

Open AccessArticle

Application of Commercial Surface Pretreatments on the Formation of Cerium Conversion Coating (CeCC) over High-Strength Aluminum Alloys 2024-T3 and 7075-T6

by Juan Jesús Alba-Galvín, Leandro González-Rovira, Francisco Javier Botana, Maria Lekka, Francesco Andreatta, Lorenzo Fedrizzi and Manuel Bethencourt

Metals 2021, 11(6), 930; https://doi.org/10.3390/met11060930 - 07 Jun 2021

Cited by 9 | Viewed by 2378

Abstract

The selection of appropriate surface pretreatments is one of the pending issues for the industrial application of cerium-based chemical conversion coatings (CeCC) as an alternative for toxic chromate conversion coating (CrCC). A two-step surface pretreatment based on commercial products has been successfully used [...] Read more.

The selection of appropriate surface pretreatments is one of the pending issues for the industrial application of cerium-based chemical conversion coatings (CeCC) as an alternative for toxic chromate conversion coating (CrCC). A two-step surface pretreatment based on commercial products has been successfully used here to obtain CeCC on AA2024-T3 and AA7075-T6. Specimens processed for 1 to 15 min in solutions containing CeCl₃ and H₂O₂ have been studied by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), glow discharge optical emission spectroscopy (GDOES), potentiodynamic linear polarization (LP), electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS) tests. SEM-EDX showed that CeCC was firstly observed as deposits, followed by a general coverage of the surface with the formation of cracks where the coating was getting thicker. GDOES confirmed an increase of the CeCC thickness as the deposition proceed, the formation of CeCC over 7075 being faster than over 2024. There was a Ce-rich layer in both alloys and an aluminum oxide/hydroxide layer on 7075 between the upper Ce-rich layer and the aluminum matrix. According to LP and EIS, CeCC in all samples offered cathodic protection and comparable degradation in chloride-containing media. Finally, the NSS test corroborated the anti-corrosion properties of the CeCC obtained after the commercial pretreatments employed. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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20 pages, 5271 KiB

Open AccessArticle

Frequency Analysis of Transients in Electrochemical Noise of Superalloys Waspaloy and Ultimet

by Jesús Manuel Jáquez-Muñoz, Citlalli Gaona-Tiburcio, Jose Cabral-Miramontes, Demetrio Nieves-Mendoza, Erick Maldonado-Bandala, Javier Olguín-Coca, Francisco Estupinán-López, Luis Daimir López-León, José Chacón-Nava and Facundo Almeraya-Calderón

Metals 2021, 11(5), 702; https://doi.org/10.3390/met11050702 - 25 Apr 2021

Cited by 7 | Viewed by 1938

Abstract

Nickel or Cobalt-based superalloys represent an important class of engineering materials, finding widespread application in critical components within the gas turbine engines used for jet propulsion and electricity generation. This research aimed at the frequency analysis of transients in electrochemical noise of Waspaloy [...] Read more.

Nickel or Cobalt-based superalloys represent an important class of engineering materials, finding widespread application in critical components within the gas turbine engines used for jet propulsion and electricity generation. This research aimed at the frequency analysis of transients in electrochemical noise of Waspaloy and Ultimet superalloys, immersed in 3.5 wt.% in H₂SO₄ and NaCl solutions at two different temperatures, 25 and 60 °C. Localized corrosion behavior of superalloys was assessed using the electrochemical noise technique (EN) according to ASTM-G199 standard. Three different statistical methods filtered the EN signal, and the polynomial method was employed to obtain the noise resistance (R_n), the localization index (LI), skew and kurtosis, and the power spectral density analysis (PSD). Results indicate that the current and potential noise transients have a better behavior with better clarity when a polynomial is used to show a localized corrosion kurtosis for both superalloys. Full article

(This article belongs to the Special Issue Corrosion and Protection in Aeronautical Alloys)

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