Process Features and Corrosion Performance in Phosphating as Related to Additive Functionality
نویسنده
چکیده
he benefits of phosphate pretreatT ments for improving the resistance of ferrous and nonferrous metals to the onset and spread of corrosion is well known.'.2 Increased stress on quality of finishes, the need for process versatility, and stringency of specifications have led to modifications of conventional phosphating formulations and have prompted the need-based development of new baths. The inclusion of specific additives has often been the basis of these developments. Among the earliest examples of the use of additives to improve the phosphating process was the introduction of oxidizing agents as accelerators in phosphating baths to reduce process time. Since then, several ~ r g a n i c , ~ inorganic4 and polymeric5 compounds have been added to phosphating baths to improve one or more specific attributes of the phosphate coatings obtained from them. The inherent capability of surfaceactive agents to improve surface cleanliness: to refine grain size, and to impart hydrophobicity on metal surfaces by forming films on them? suggests that their inclusion in phosphating baths would produce multifaceted improvements 'in the properties of phosphate coatings. Among several types of surfactants considered for use as additives in phosphating baths, flotation surfactants having the capability to impart surface hydrophobicity to metal surfaces-a property as significant in stifling the onset and spread of corrosion as it is in conventional use for separating metallic minerals from ore slurries-were most suitable for this study. Our studies on a series of some popularly used surfactant collectors brought to light the significance of the functionality of the additive in determining its role in phosphating baths. The intent of this study is to relate the structural aspects of three representative congeneric flotation surfactants possessing similar 1 8-carbon aliphatic chains in their structurel-octadeTable I. Table of Additives Used
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