A surface charge model of corrosion pit initiation and of protection by surface alloying

The isoelectric point of the oxide-covered aluminum surface is an important parameter in the pitting behavior of aluminum and of aluminum binary surface alloys. Contact angle measurements show that ion implantation of Ta into Al modifies the isoelectric point of the resulting oxide film to a value w...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the Electrochemical Society 1999-08, Vol.146 (8), p.2863-2869
Main Author: MCCAFFERTY, E
Format: Article
Language:English
Subjects:
ALUMINIUM
ALUMINIUM BASE ALLOYS
Applied sciences
Corrosion
Corrosion environments
CORROSION PROTECTION
Exact sciences and technology
ION IMPLANTATION
MATERIALS SCIENCE
Metals. Metallurgy
PITTING CORROSION
TANTALUM
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The isoelectric point of the oxide-covered aluminum surface is an important parameter in the pitting behavior of aluminum and of aluminum binary surface alloys. Contact angle measurements show that ion implantation of Ta into Al modifies the isoelectric point of the resulting oxide film to a value which is intermediate between that of Al sub 2 O sub 3 and Ta sub 2 O sub 5 . The critical pitting potential is shown to be a function of the flatband potential of the oxide-covered aluminum surface. For a series of alloys where the matrix metal (and host oxide) is held fixed, the flatband potential is a function of the isoelectric point of the oxide film on the alloy surface, which in turn is a function of the isoelectric point of the oxide of the alloying element. Thus, the critical pitting potential of a binary surface alloy is related to the isoelectric point of the oxide of the alloying element in the binary alloy. Surface alloying affects the pitting potential by (i) modifying the isoelectric point of the surface so as to change the surface charge, (ii) affecting the heat of adsorption of the chloride ion, and (iii) changing the concentration of oxygen vacancies in the oxide film.
ISSN:0013-4651
1945-7111
DOI:10.1149/1.1392021