Corrosion common mistakes

All areas of the cooling water system where a specific form of damage is likely to be found are described. The corrosion or failure causes and mechanisms are also described. Especially important factors influencing the corrosion process are listed. Detailed descriptions of each failure mode are given, along with many common, and some not-so-common, case histories. Descriptions of closely related and similarly appearing damage mechanisms allow discrimination between failure modes and avoidance of common mistakes and misconceptions. 

A note of caution about roof fasteners. A common mistake is to fix a galvanised or aluminium roof in place with nails or screws of a different metal copper or brass, for instance. The copper acts as cathode, and the zinc or aluminium corrodes away rapidly near to the fastening. A similar sort of goof has been known to occur when copper roofing sheet has been secured with steel nails. As Fig. 24.6 shows, this sort of situation leads to catastrophically rapid corrosion not only because the iron is anodic, but because it is so easy for the electrons generated by the anodic corrosion to get away to the large copper cathode. 

Again, wear is the removal of material. The idea that friction causes wear and therefore, low friction means low wear, is a common mistake. Brief descriptions of five types of wear abrasive, adhesive, fatigue, chemical or corrosive, and fretting — may be found in Reference 2 as well as in other references in this article. Next, it maybe useful to consider some of the major concepts of lubrication. 

Kirby. G. N., Avoid Common Corrosion Mistakes for Better Performance, Chemical Engineering Progress, April 1997. 

Material limitations not commonly known to the architectural practitioner, which will affect design are listed. Lack of knowledge of corrosion resistant masonry construction has resulted in costly mistakes. This approach will appear sophomoric but such errors have occurred with sufficient frequency to warrant inclusion. The information is covered more specifically and in greater detail in other chapters. While redundant, it is important that the less experienced be forewarned of these limitations. 

All the compounds of Zn which are soluble in the digestive fluids behave as true poisons and solutions of the chloride (in common use by tinsmiths, and in disinfecting fluids) have also well-marked corrosive properties. When Zn compounds are taken, it is almost invariably by mistake for other substances the sulphate for E som salt, and solutions of the chloride for various liquids, gin, fluid magnesia, vine, etc. 

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