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A set of passivated tinplates coated with organic lacquers as used for internal coatings on cans is examined. Adhesion is measured using a butt-joint test and the results of failure load and percent area lacquer removal analysed in order to grade adhesion performance. Fracture behaviour is determined by the surface structure of the tinplates where a defect distribution common to all types is identified by Weibull analysis as responsible for failure initiation. Differences in fracture behaviour seen in the mechanical test results are revealed by examination of the fracture surfaces using optical microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The samples with good lacquer adhesion show a positive relationship between failure load and lacquer removal which is not evident in the samples with poor lacquer adhesion. The latter exhibit weak bonding between the passivation layer and tinplate and on examining those areas of fracture surface where tinplate is revealed the fracture is seen to have propagated at this interface whereas those samples with good adhesion had failed near the lacquer-passivation layer interface within the lacquer. Passivation layers are characterised using X-ray photoelectron spectroscopy and transmission electron microscopy. Differences in composition relating to specific tin oxides and chromium oxides are correlated with adhesion performance and models for the structure of passivation layers and failure mechanisms are proposed.

The preparation, type and stability of emulsions stabilised solely by solid silica particles has been investigated in detail using a combination of conductivity, stability, light diffraction, optical microscopy and contact angle measurements. The wettability of the particles in situ at the oil-water interface plays a major role in such systems. The stability of aqueous colloidal dispersions in the presence of various electrolytes and over a range of pH is shown to be important in determining the stability of toluene-in-water emulsions formed from them. Partial flocculation of the silica dispersions enhances the emulsion stability whereas strong flocculation results in unstable emulsions. Inversion of emulsion type occurs via two mechanisms. Catastrophic inversion of water-in-oil emulsions stabilised by hydrophobic silica particles occurs upon increasing the volume fraction of water in the system. Transitional inversion of emulsions at fixed volume fraction of water has been achieved by varying the mass fraction of hydrophilic (or hydrophobic) particles in systems containing particle mixtures. Neither inversion mechanism exhibits hysteresis, in contrast to surfactant-stabilised systems. The energy of attachment of a particle to the oil-water interface is shown to be dependent on the contact angle and the interfacial tension. The contact angle was varied by changing the hydrophobicity of the silica particles. Particles of intermediate hydrophobicity were most effective at stabilising emulsions which is thought to be due to the contact angle at the oil-water interface being close to 90°. The interfacial tension was affected by changing the nature of the oil phase or by'replacing water with various polar liquids. Undecanol-water emulsions stabilised by silica particles of intermediate hydrophobicity break down via gel formation followed by coalescence. The wettability of the silica surface was varied in situ by varying the pH of the aqueous phase. Increasing the pH causes dissociation of silanol groups, which increases the affinity of the particles for the aqueous phase. The type and stability of emulsions and the contact angle of an aqueous drop under toluene on hydrophobically modified glass slides were measured as a function of pH. The results are modelled using simple theory. The wettability of hydrophobic pigment surfaces is dependent on the type and concentration of added surfactant. The findings are discussed in terms of surfactant adsorption at the relevant interfaces.