Influence of Cr addition on the electrochemical behavior of Ni –base metallic glasses in HCl

 

S.T. Arab1,  K. M. Emran2*

1Department of Chemistry , Girls’ College of Education King Abdul Aziz Uuniversity, P.O(2321) , Jeddah 21451 , Kingdom Saudi Arabia (s.t.arab@hotmail.com).

2Department of Chemistry , Girls’ College of Education, Taibah university Al-Madinah Al-Monawarah ,Kingdom Saudi Arabia.(k_imran2000sa@yahoo.co.uk)

* Corresponding author. E-mail: k_imran2000sa@yahoo.co.uk

Received: 07 April 2008; revised version accepted: 13 July 2008

 

Abstract

   The contribution of Cr concentration on the corrosion resistance of nickel – metalloids glassy alloys (Ni92.3Si4.5B32, Ni82,3Cr7Fe3Si4.5B3.2 and Ni75.5Cr13Fe4.2Si4.5B2.8) was studied by electrochemical methods , SEM and XPS analyses. The corrosion kinetics and passivation behavior was studied . The study also focused on the HCl concentration and its effect on the corrosion rate, passivation ability and pitting susceptibility on  nickel base glassy alloys surface. Cr – free alloy has no ability to reach passive stage and  continues in active dissolution.  The high  corrosion  resistance of Cr contains alloys  is  based  on  the formation  of a protective layer on the  surface  which acts as a diffusion barrier against alloy dissolution. The addition of  Cr  enhances  the  corrosion  resistance  due  to  spontaneous  passivation. The  passive  film  on the Cr  containing  alloys  consists  mainly  chromium  oxyhydroxide.

 

Keywords: Metallic glasses; Passivity; Role of chromium; Spontaneous passivation; Polarization; EIS; XPS, SEM.

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