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Paint has long been used for the protection of iron and steel against corrosion.
From the electrochemical theory of corrosion it follows that corrosion can be stopped by suppressing either the cathodic or the anodic reaction, or by inserting between the cathodic and anodic areas a large resistance, which impedes the movement of ions. Calculations indicate that paint films are so permeable to water and oxygen that they cannot suppress the cathodic reaction. Paints can inhibit corrosion by modifying the anodic reaction; for this to occur the pigment must be either metallic, or basic, or soluble. In general, paint films protect by virtue of their high electrolytic resistance; they readily acquire a charge, consequently they are relatively impermeable to ions. Soap formation is beneficial, since it renders the film less permeable to electrolytes; it also yields soluble inhibitive degradation products, which have been identified.
Mayne and coworkers have carried out intensive studies on the electro‐chemical behaviour of anti‐corrosive paint systems. More recently they have shown that the paint…
Mayne and coworkers have carried out intensive studies on the electro‐chemical behaviour of anti‐corrosive paint systems. More recently they have shown that the paint films possess ionogenic sites which become ionised by the absorption of water or moisture and thus become selectively permeable to ions and the process of ion exchange follows. They have also studied the variations in the electrical resistance of a soya alkyd film as a function of the uptake of metallic ions. Bacon et. al. used electrical resistance measurements in assessing the anti‐corrosive properties of some three hundred paint systems, using mild steel panels coated with pigmented paint media as one of the electrodes of the test cell and have shown that the method is quite suitable for predicting their actual performances in marine environments. Khullar and Ulfvarson have determined the ion exchange capacities and ion exchange rates of about twenty different paint media films and drawn a sort of relation between their ionic behaviour and anti‐corrosive abilities.
The above Congress, being held at the Imperial College of Science and Technology, London, from April 10–15, has been described as likely to be the corrosion event of the…
The above Congress, being held at the Imperial College of Science and Technology, London, from April 10–15, has been described as likely to be the corrosion event of the decade. Size alone is no criterion, though over 80 papers are being presented, but the standing of many of the corrosionists associated with the Congress is, perhaps, the best indication of the truth of this statement. Summaries and abstracts of some of the papers appear in the following pages. More will be published in next month's issue.
The corrosion of metals can be reduced or prevented by influencing the electrode processes of electrochemical corrosion cells with suitable chemical additions to the corrosive electrolyte. It is the purpose of these articles to consider the mechanism of inhibition, and the applications and limitations of typical inhibitors. This first article is devoted to a consideration of the principles of inhibition in aqueous neutral solutions.
In the Scandinavian countries there is growing awareness of the need to intensify the fight against corrosion by co‐operative research and the exchange of information…
In the Scandinavian countries there is growing awareness of the need to intensify the fight against corrosion by co‐operative research and the exchange of information. This culminated in the Scandinavian Corrosion Con‐ference held in Copenhagen last month. A number of papers were presented, mostly by Danish scientists. There was also a contribution by a British scientist. Here are summaries of these papers, specially translated and prepared for CORROSION TECHNOLOGY.
Summary A new technology for electropainting fabrications such as car bodies, by reversing the conventional polarity, was introduced into the U.K. market in 1979. It was…
Summary A new technology for electropainting fabrications such as car bodies, by reversing the conventional polarity, was introduced into the U.K. market in 1979. It was claimed that the new method greatly increased the resistance to corrosive attack in service of such items, but the implementation of the acid paint system used was recognised as a potential source of failure for customary and proven electropaint tank linings used with the original basic protection primer. It was essential that a newly formulated resin tank lining was provided to meet the needs of major consumers of the new cathodic painting process and this dissertation outlines the method chosen and the constraints and risks which applied. A series of trial formulations were prepared incorporating the theory and practice of polymer technology for a new and novel development which would meet the challenge of a brand new technology. The high financial risk involved in possible failure together with the limited time available for assessment was weighted against the potential of a new market, and both commercial and technical requirements were satisfied by extending the theory of surface coating science into practice, through laboratory evaluation.
Corrosion has been defined as the destruction of metal by chemical or electrochemical reaction with its environment. Methods of corrosion control become more and more…
Corrosion has been defined as the destruction of metal by chemical or electrochemical reaction with its environment. Methods of corrosion control become more and more important as we are increasingly concerned about conserving our natural resources. For effective control of corrosion, we must have a thorough understanding of its nature and methods of measurements. Little correlation exist between laboratory tests and field performance. Atmospheric exposure tests are required to determine the relative aggressiveness of the environment to a variety of materials that might be selected for use. The development of data for this purpose makes possible a suitable selection of materials. Atmospheric small scale tests can often be made the basis of positive statement about the durability of metals, alloys, metal couples and painted metals on large structures and it needs very careful planning and preparation.