Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking Load Method

10.1520/g0139 ◽  
2008 ◽  
Author(s):  
Keyword(s):  
Aluminum Alloy ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Breaking Load ◽  
Corrosion Cracking ◽  
Test Method ◽  
Cracking Resistance

Preparation of Electroless Nickel-Phosphorous-TiO2 Composite Coating for Improvement of Wear and Stress Corrosion Cracking Resistance of AA7075 in 3.5% NaCl

2015 ◽  
Vol 656-657 ◽  
pp. 74-79 ◽  
Author(s):  
Cheng Kuo Lee ◽  
Chung Sheng Chang ◽  
An Hung Tan ◽  
Ching Yi Yang ◽  
Sheng Long Lee
Keyword(s):  
Aluminum Alloy ◽  
Stress Corrosion ◽  
Composite Coating ◽  
Stress Corrosion Cracking ◽  
Pitting Corrosion ◽  
Corrosion Cracking ◽  
Boiling Water ◽  
Cracking Resistance ◽  
Electroless Ni ◽  
Sealing Treatment

In this study nanoTiO2 particles were incorporated into the electroless plating solution to prepare Ni-P-TiO2 composite coating on anodized AA7075 aluminum alloy to improve the wear and stress corrosion cracking resistance of the coated alloy in 3.5%NaCl solution. The anodized AA7075 aluminum alloy was also performed by a boiling water sealing treatment for comparison. The wear and stress corrosion cracking (SCC) characteristics were investigated using a self-designed block-on-ring machine and slow strain rate test. The effect of corrosion was evaluated by electrochemical polarization measurements. The surface morphology, element composition and surface hardness of the coating were analyzed by scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDS) and Vicker′s hardness tester. Experimental results indicated that after boiling water sealing treatment the resistance properties of the anodized AA7075 aluminum alloy were further improved. The anodizing treatment of AA7075 aluminum alloy gave a thick film with high porosity. The porous film efficiently improved the cohesion, adhesion and hardness of the electroless Ni-P composite coating. Therefore, the electroless Ni-P composite coating deposited on the anodized AA7075 aluminum alloy offered a superior wear, pitting corrosion and stress corrosion cracking resistance properties than both anodizing and sealing treatment. By comparison with Ni-P and Ni-P-TiO2 coatings the incorporation of TiO2 resulted in a more uniform and crack-free surface structure of the composite coating. This is responsible for the higher hardness, better wear, pitting corrosion and stress corrosion cracking resistance of the electroless Ni-P-TiO2 coating.

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