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Magnesium ferrite pigments were evaluated as active pigments in anticorrosive water‐borne paints. The study includes the use of two different anticorrosive pigment volume concentration (APVC), 15 and 25 per cent and fixed the Q value (the pigment volume concentration/critical pigment volume concentration ratio) in both paint formulations. Epoxy and acrylated alkyd resins were used as binders. The paints were evaluated by accelerated salt spray tests, corrosion tests in condensed water and sulphur dioxide chambers and electrochemical evaluations. The results obtained were compared with reference paints containing zinc ferrite and zinc phosphate pigments. Ferrite pigments passivate the carbon steel directly in the case of neutral epoxy resin binder or indirectly due to the soaps produced as a result of reaction with the acidic acrylated alkyd resin binder. A lower per cent, i.e. 15 per cent of APVC was found to be sufficient to provide satisfactory anticorrosion protection.

Salts of aluminium and calcium such as stearates, octoates and naphthenates, are used to impart structure to oleoresinous paints. Alternatively, aluminium alcohoiates can be used as reactive intermediates which form salts by reaction with the medium. The use of these materials is generally restricted to flat or semi‐gloss paints and storage instability is sometimes encountered. A chlorinated rubber paint which contains titanium, kaolin, talc, a chloroparaffin plasticiser, and a solvent blend of hexyl acetate and xylene, is rendered thixotropic using a 1% level of aluminium stearate addition. The product is suitable for applying as thick corrosion‐resistant coatings to metals.

The degradation of coatings is, of course, a major area of interest for paint chemists. One of the coatings that degrades, much to the consumer's despair, is automotive coatings. The degradation of an acrylic‐melamine, cross‐linked coating containing finely dispersed pigment, metallic flake, and other additives was studied by English and Spinelli (Organic Coatings and Applied Polymer Science Proceedings, preprints of papers presented by the Division of Organic Coatings and Plastics Chemistry at the American Chemical Society, 185th National Meeting, Seattle, Washington, March 20–25, 1983, p. 733) using diffuse reflectance infra‐red spectroscopy. They found that the degradation is facilitated near the surface by ultra‐violet light and that there is a cleavage of the nitrogen‐carbon bond on the methoxymethylamino moities. Much of the degradation appears to take place at the surface level and degradation of bonds does not lead to significant self‐condensation of the degraded materials. The authors indicate that they are currently using MMR techniques to identify the products of degradation.

Some of the properties of paints based on alkyd emulsion are discussed and they are divided into four categories. Colloidal stability of water based paints is predominantly governed by osmotic and electrostatic repulsion of both the binder and the pigment particles. The rheological behaviour of paints based on binder dispersions should be optimised by using thickeners with the proper mix of hydrophilic and hydrophobic polymeric segments. Stability of drying properties of alkyd emulsion paints upon storage can be strongly improved by preventing the use of ketoximes as anti‐skinning agents and by selecting the proper driers. Properties of the dried paints depend strongly on the process of film formation. The protective and aesthetical quality of films based on binder dispersions is governed by the key parameters of the resin that is within the droplets; viscosity, miscibility and the ability of the binder to undergo crosslinking. To obtain the total package of desired properties of water based paints it is necessary that all of the paint components are adjusted to each other. This can only be done if the companies that develop and market the raw materials work closely together. The use of fundamental knowledge in such co‐makerships results in better and faster developments.

Organophilic Sylodex Bentonites are organically treated forms of the clay mineral montmorillonite. The latter is present in the form of microscopically small platelets. The platelets are characteristic of the crystalline structure of the montmorillonite. The chemical composition is that of an aluminium hydrosilicate in which the silicon, aluminium and oxygen atoms are arranged in 3 layers (see Fig. 1). The outer layers consist of SiO2‐tetrahedra and the inner layers of (AlO4(OH)2) octahedra. An idealized initial structure of the precursor of montmorillonite exhibits the following neutral formula:

In practice we often find structures of different paint layers applied one after another as e.g. in multilayerpaint systems or in case of repair painting. The good adhesion of the individual paint layers is of vital importance to the functioning of the whole system.

The author discusses several examples of paint systems that failed, not because of the quality of the paint, but from defects or complications during application. Metal pretreatment, air pollution, and method of application are all factors to be considered. Effects of marine and industrial environments are discussed.

A suggestion that instead of retarding corrosion it might be a good idea to think of ways of accelerating it, was made by Dr Norbert Ibl, President of the Scientific Committee, at the opening ceremony of the 8th Congress of the International Union for Electrodeposition and Surface Finishing held recently in Basle.