Corrosion of Zinc Coated Steel: An Atomic Force Microscopy Study of Galvanised and Galvannealed Steels
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Accession number;05A0305028
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| Title;Corrosion of Zinc Coated Steel: An Atomic Force Microscopy Study of Galvanised and Galvannealed Steels |
| Author;
FITZPATRICK M F
(Honda R&d Europe, Gbr)
NAKAZAWA Y
(Honda R&d Europe, Gbr)
CASTLE J E
(Univ. Surrey, Guildford, Gbr)
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Journal Title;Honda R&D Tech Rev
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Journal Code:L0353A
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ISSN:0915-3918
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VOL.17;NO.1;PAGE.107-116(2005)
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| Figure&Table&Reference;FIG.14, TBL.1, REF.8 |
| Pub. Country;Japan |
| Language;English |
| Abstract;Over the past 20 years the automotive industry has constantly improved vehicle corrosion behaviour by exploiting the benefits of zinc coated steels. The application of zinc coated steel, however, does have considerable impact on processes within the automotive industry, the choice of coating type, therefore, can differ between OEM. Using the surface sensitive technique of Atomic Force Microscopy (AFM) the local corrosion behaviour of galvanised steel (GI) and galvannealed (GA) has been compared. Three sample models have been exposed to 5 wt% sodium chloride solution, for different times, to simulate cut edge, stone chipping and galvanic coupling corrosion behaviour. AFM was used to determine the volume of material loss for each time interval which could then be related to an absolute measure of corrosion rate. By converting corrosion rate to current density values the degree of electrochemical activity of the GI and GA systems were compared. For all experimental models GA showed lower corrosion densities compared to GI. The cut edge specimens show GI to have up to 7 times the current density of GA after 256 minutes. The coupled samples magnify this difference further with almost no material loss to the GA coating but a greatly increased corrosion rate for GI. This study has confirmed that, by using the specialised technique of AFM in an innovative way, GA outperforms GI, where the zinc coating has been damaged, with its coating sacrificially corroding at a slower rate. (author abst.) |
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