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Title: Development and application of the three-dimensional scanning vibrating electrode technique for the monitoring of localised corrosion on galvanised automotive strip steels
Author: Wilson, B. P.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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The Scanning Vibrating Electrode Technique (SVET) represents an excellent tool to investigate localised corrosion mechanisms, having superior sensitivity and spatial resolution to the Scanning Reference Electrode Technique (SRET). It also measures a quantity directly proportional to the normal component of current flux making it also ideal for quantification of corrosion. The technique to date has been limited to planar samples and as such any welds would be ground flat and formed components cannot be studied. This is clearly not desirable in particular when dealing with thin (10|jm) zinc coatings. In Chapter 4 this new 3-D SVET set-up was then used to investigate the effects that simple forming operations have on corrosion behaviour of a number of galvanised coatings with particular emphasis on galvanneal (an iron-zinc coated steel). Here the doming process revealed iron leading to localisation of the anodic and cathodic processes. Chapters 5 and 6 detail work performed on the two major types of joining technology currently utilised in the automotive industry namely spot welding and laser welding on local corrosion activity. The findings illustrate the effect that the laser welding of differently coated steels can have on the amounts of corrosion activity due to bimetallic corrosion. For instance combination of Electro Zinc and Iron Zinc alloy coatings lead to elevated attack on the former coating. The impact that the both spot weld lifetimes and welding current procedures have on the observed corrosion mechanisms of galvanised steels is also demonstrated. Initial brassing in the spot welds and zinc enrichment lead to cathodic and anodic activity localisation and poor weld quality is also accompanied by inferior corrosion protection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Eng.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available