Abstract
The present work introduces an automated corrosion test for coating systems on magnesium alloys, which is based on the titration method introduced by General Motors [1], in which the dissolution rate of magnesium is determined from the amount of HCl added to a sodium chloride solution required to maintain a constant pH value. It is demonstrated that this technique allows a screening of various types of coatings on magnesium alloys yielding much more information than a standard salt spray test or a simple standard immersion test. The main advantage lies in the continuous measurement of the corrosion rate without disturbing the corrosion system and without the need for cleaning the specimens from corrosion products in order to measure weight changes.
Kurzfassung
Der vorliegende Beitrag stellt ein automatisiertes Prüfverfahren zur Korrosionsprüfung von Beschichtungssystemen auf Magnesiumlegierungen vor. Es beruht auf dem von General Motors eingeführten Titrationsverfahren, in dem die Auflösungsrate von Magnesium anhand des Anteiles von Salzsäure bestimmt wird, die einer Natriumchloridlösung zugegeben werden muss, um den pH-Wert konstant zu halten. Es wird gezeigt, dass diese Methode eine Prüfung von verschiedenen Beschichtungstypen auf Magnesiumlegierungen erlaubt und viel mehr Informationen zur Verfügung stellt als ein standardisierter Salzsprühtest oder Eintauchversuch. Der Hauptvorteil des Verfahrens liegt in der kontinuierlichen Messung der Abtragsrate, ohne das Korrosionssystem an sich zu stören und ohne die sonst notwendige Reinigung der Probe zur Messung von Gewichtsveränderungen vornehmen zu müssen.
Literatur
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