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Automotive phosphating technology 1975-1995
Technical Paper
1993-10-0037
Sector:
Language:
English
Abstract
Both paint appearance and corrosion performance of automobiles
depend on the application of a high quality surface conversion
coating. The impact of the choice of metals for automobile body
construction on these product properties and environmental concerns
have driven developments in surface treatment technology. The
performance of steel as an exterior automotive surface was
maximized by conversion coatings with a high iron content. When the
predominant use of cold rolled steel was replaced by the
introduction of electrogalvanized and other coated products,
changes in cleaners and further changes in phosphate bath and
coating composition improved the performance of these new surfaces.
The tri-cation (Zn, Ni, Mn) phosphating systems were introduced to
provide the highest quality coating in a mixed metal system. In
recent years, changes in materials of construction have slowed
because corrosion goals have been met and, as a consequence,
industry needs for new technology have shifted. Operational and
environmental considerations now play a larger role among the
current driving forces in the development of new conversion coating
products.
This paper traces the sequence of improvements which have been
introduced in automotive pretreatment and demonstrates these
improvements with results from accelerated corrosion tests.