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In this second and concluding part of his article, Mr. Stanners discusses the choice of paints, paint formulation, the paint system, and, finally, when and how to paint. The first part of the article ‘Preparing to Paint’ appeared in our August issue.

During the second day of the symposium on ‘The Protection of Structural Steel’ interest again centred on the comparative advantages of paint and metal coatings. Speakers discussed the composition of good paint protective systems and the application of sprayed metal coatings, and some consideration was given to the relative cost of the two methods. A report of the papers read during the first day was given in the May issue of CORROSION TECHNOLOGY.

For many years the effect of sulphuric anhydride in the atmosphere has been recognised, such as in the report by Thomson. As an example of this, consider some of the work reported by Hudson and Stanners, who exposed iron and steel to copper in a variety of environments. When they studied the results, they found a close relationship between the degree of corrosion and the amount of SO2 present, whereas the effect of chlorides was restricted to a narrow test area close to the sea.

Dr. Hudson Retires DR. J. C. HUDSON, who has been in charge of B.I.S.R.A.'s research on corrosion for the last 15 years—ever since its formation—retired last month. He will, however, act as consultant to both the corrosion advice bureau and the chemistry department.

The corrosion of metal structures outdoors is a problem common to almost all industries, for such structures range from bridges to window frames. Painting is the most widely used method of protection, but to get the best results full use must be made of the separate skills of the designer and engineer, the painting contractor, the paint manufacturer and the foreman and painter on the job. Nor must the important contribution of those who prepare the metal to receive the paint be forgotten. All these aspects of the successful use of paint to prevent corrosion are considered in this authoritative and practical article.

Zinc coatings are applied commercially by hot‐dipping, electro‐deposition, metal‐spraying, cementation and vacuum deposition (see Table 5). Galvanizing (zinc hot‐dipping) has been done for more than 200 years now and is undoubtedly the most widely‐used form of metal coating. The production and pro‐perties of these coatings have received intensive study over the last 10 years; much of this has been reported at the ‘International Conferences on Hot‐Dip Galvanizing’.

THE EXTENSIVE use of steel can be attributed to its many physical and mechanical properties and low cost when compared to other materials. It has, however, one major disadvantage in that it will corrode in many environments.

Paint drying is a very important process in an industry where shorter drying time for productivity and lower energy consumption for production cost are required while maintaining the product’s painting quality. In the present study, a drying process in a line-type paint drying furnace equipped with nozzles for hot air supply and moving conveyer belt to dry painted automotive parts is numerically simulated for the flow and heat transfer inside the furnace to evaluate the quality of the drying or baking at the end of the drying process in a production line.

A baking window for a specific paint is used for judging the local degree of baking (DOB) of the painted parts, which can be useful to identify under-baked or over-baked locations of the painted parts, and hence the quality of the baking process.

Numerical results of a time history of temperatures at two monitoring points on the painted parts were obtained and compared to the measured data in an actual furnace and showed good agreement. Three types of paints were considered in the present study and numerical results showed different drying characteristics. In addition to the original furnace nozzle configuration, two more furnace nozzle configurations with different numbers, direction and speed of hot air supply were simulated to improve the furnace’s drying performance. As a result, a newly suggested nozzle configuration with quick drying paint can give us a remarkable improvement in surface averaged DOB compared to the original nozzle configuration with original paint.

The present simulation technique and DOB methodology can be used for the optimal design of a drying furnace.

Sprayed metal coatings have a characteristic structure which greatly influences their behaviour in corrosion processes. The coatings are built up from tiny particles of metal, of the order of 20 microns diameter, produced by atomising molten metal in a stream of compressed air. The metal is supplied to the spraying pistol either as a wire or a powder and is melted in an oxygen‐fuel gas flame. The metals of low melting point, including zinc and aluminium, are also applied by a pistol which receives molten metal from a heated reservoir.

This article is primarily concerned with those metallic diffusion coatings that are applied for the protection of iron and steel. It will be presented in three parts: 1. Aluminium coatings. 2. Chromium coatings. 3. Zinc coatings. Special reference is made in each part to the available methods of application, the coatings' composition and structure, their physical properties, and their corrosion and oxidation resistance.