Preparation of electroless nickel-phosphorous-TiO2 composite coating for improvement of wear and stress corrosion cracking resistance of AA7075 in 3.5% NaCl

Cheng Kuo Lee, Chung Sheng Chang, An Hung Tan, Ching Yi Yang, Sheng Long Lee

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

In this study nano TiO2 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.

Original languageEnglish
Title of host publicationRecent Development in Machining, Materials and Mechanical Technologies
EditorsJyh-Chen Chen, Usuki Hiroshi, Sheng-Wei Lee, Yiin-Kuen Fuh
PublisherTrans Tech Publications Ltd
Pages74-79
Number of pages6
ISBN (Print)9783038354956
DOIs
StatePublished - 2015
EventInternational Conference on Machining, Materials and Mechanical Technologies, IC3MT 2014 - Taipei City, Taiwan
Duration: 31 Aug 20145 Sep 2014

Publication series

NameKey Engineering Materials
Volume656-657
ISSN (Print)1013-9826
ISSN (Electronic)1662-9795

Conference

ConferenceInternational Conference on Machining, Materials and Mechanical Technologies, IC3MT 2014
Country/TerritoryTaiwan
CityTaipei City
Period31/08/145/09/14

Keywords

  • AA7075 alloy
  • Corrosion
  • Electrochemical polarization
  • Electroless Ni-P
  • SCC
  • SSRT

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