Comparative Study on the Time-Dependent Electrochemical Corrosion Behavior of Unmodified and Sr-Modified Al-7Si-0.3Mg (A356) Alloys

Öz

As-cast Al-Si-Mg alloys are widely used in the production of lightweight components with complex geometries owing to their high corrosion resistance, excellent castability, and improved mechanical properties. This study investigates the influence of strontium (Sr) modification on the time-dependent corrosion behavior of die-cast Al-7Si-0.3Mg (A356) alloy. For this purpose, both unmodified and 0.02 wt.% Sr-modified alloys were systematically examined in a 3.5 wt.% NaCl solution over different immersion times (1, 24, 48, 72 and 120 h). To examine the corrosion behavior of the alloys, electrochemical analyses were carried out employing potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results demonstrate that 0.02 wt.% Sr modification increases the initial corrosion rate compared to the unmodified A356 alloy, due to intensified micro-galvanic interactions. Potentiodynamic polarization results indicate that the unmodified alloy exhibits the most favorable corrosion behavior at the initial immersion time (1 h), as evidenced by the lowest corrosion current density (0.050 μA·cm⁻²). Consistently, EIS results reveal that the Sr-modified alloy has an approximately 70.3% lower charge transfer resistance (Rct), indicating higher initial electrochemical activity. At longer exposure times, the Sr-modified alloy exhibits enhanced corrosion behavior, due to the formation of a more stable and protective corrosion product layer.

Anahtar Kelimeler

• A356 alloys
• Strontium modification
• Time-dependent corrrosion behavior
• Potentiodynamic polarization
• EIS

Destekleyen Kurum

There is no conflict of interest in this study.

Etik Beyan

The author declares that the materials and methods employed in this study do not require ethical committee approval or any specific legal authorization.

Teşekkür

The author has no acknowledgments to declare

Modifiye Edilmemiş ve Sr ile Modifiye Edilmiş Al-7Si-0.3Mg (A356) Alaşımlarının Zamana Bağlı Elektrokimyasal Korozyon Davranışının Karşılaştırmalı İncelenmesi

Öz

Döküm halinde (as-cast) Al-Si-Mg alaşımları, yüksek korozyon direnci, mükemmel dökülebilirlik ve geliştirilmiş mekanik özellikleri sayesinde karmaşık geometrilere sahip hafif bileşenlerin üretiminde yaygın olarak kullanılmaktadır. Bu çalışmada, stronsiyum (Sr) modifikasyonunun, basınçlı döküm yöntemiyle üretilmiş Al-7Si-0.3Mg (A356) alaşımının zamana bağlı korozyon davranışı üzerindeki etkisi incelenmiştir. Bu amaçla, modifiye edilmemiş ve %0.02 (ağırlıkça) Sr ile modifiye edilmiş alaşımlar, %3,5 NaCl çözeltisi içerisinde farklı daldırma sürelerinde (1, 24, 48, 72 ve 120 saat) sistematik olarak değerlendirilmiştir. Alaşımların korozyon davranışını belirlemek amacıyla, potentiyodinamik polarizasyon ve elektrokimyasal empedans spektroskopisi (EIS) analizleri gerçekleştirilmiştir. Elde edilen sonuçlar, %0.02 Sr modifikasyonunun, mikro-galvanik etkileşimleri artırması nedeniyle başlangıç korozyon hızını modifiye edilmemiş A356 alaşımına kıyasla yükselttiğini göstermektedir. Potentiyodinamik polarizasyon sonuçları, modifiye edilmemiş alaşımın başlangıç daldırma süresinde (1 saat) en düşük korozyon akım yoğunluğu (0.050 μA·cm-2) ile en iyi korozyon performansını sergilediğini ortaya koymuştur. Bununla uyumlu olarak, EIS sonuçları Sr ile modifiye edilmiş alaşımın yaklaşık %70,3 daha düşük yük transfer direnci (Rct) değerine sahip olduğunu ve bunun daha yüksek başlangıç elektrokimyasal aktiviteye işaret ettiğini göstermektedir. Bununla birlikte, daha uzun daldırma sürelerinde Sr ile modifiye edilmiş alaşımın, daha kararlı ve koruyucu bir korozyon ürünü tabakasının oluşumu sayesinde gelişmiş korozyon direnci sergilediği belirlenmiştir.

Anahtar Kelimeler

• A356 alaşımı
• Stronsiyum modifikasyonu
• Zamana bağlı korozyon davranışı
• Potansiyodinamik polarizasyon
• Elektrokimyasal empedans spektroskopisi

Destekleyen Kurum

Bu çalışmada herhangi bir çıkar çatışması yoktur.

Etik Beyan

Yazar, bu çalışmada kullanılan materyal ve yöntemlerin etik kurul onayı veya herhangi bir özel yasal izin gerektirmediğini beyan etmektedir.

Teşekkür

Yazarın beyan edeceği herhangi bir teşekkür bulunmamaktadır.

Kaynakça

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