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SCIENCE AND INDUSTRY. 
The Corrosion of Condenser Tubes.” 
Fifth Report of the Corrosion Committee of the Institute of Metals. 
|The Institute of Science and Industry has recently been requested 
by large industrial organizations in Australia to investigate this problem 
in Australia. | 
The present report is confined to the corrosion of condenser tubes 
—mainly 70: 30 brass—and is a study. of the practical problems of 
corrosion in condensers under service conditions, employing either sea 
water or fresh water. It is divided into four sections. 
The first section deals with what has been called the diagnosis of 
condenser-tube corrosion. The procedure to be followed in withdraw- 
ing and preparing a tube for examination is described, also the 
symptoms or appearances within the tube which correspond to each 
of the five main types into which the practical problems of corrosion 
under fresh-water or sea-water conditions have been classified. The 
importance of additional information concerning (@) the water supply, 
_and (b) the corroded tubes towards elucidating the cause of corrosion 
is shown and emphasized. This information, which is specified, has 
rarely been obtainable in the past, particularly as regards the water 
supply, and this may partly account for the lack of appreciation of 
the importance in corrosion troubles of the conditions existing within 
the plant. These conditions frequently vary very much from time to 
time, and it is shown that, although the conditions which fayour 
accelerated corrosion may be present for but short periods at irregular 
intervals, and consequently may not be easily detected, the effect on 
the tubes may still be very serious. Also in certain cases it is shown 
that accelerated localized corrosion. may persist after the initiating 
conditions have disappeared. 
The second section is devoted to a consideration of certain features 
in the structure of condenser tubes, since an appreciation of these is 
of great value in following the mechanism of the types of corrosion 
studied later. Attention is principally directed to the presence on 
the tubes of a surface layer consisting of structureless and highly dis- 
torted metal. This layer. has undoubtedly a greater resistance to 
corrosion by saline and fresh waters than the underlying crystalline 
metal, so that whenever this is penetrated corrosion will proceed at an 
increased rate. The layer has been stripped from a number of tubes 
of different composition. Its thickness is usually of the order of 
0.01 mm., and indications have been obtained that its composition may 
be somewhat different from that-of the underlying metal. 
In the third section, the five main types of brass condenser tube 
corrosion are considered separately in detail. 
Type I., General Thinning—This type may be considered as an 
accelerated form of the complete corrosion which normally occurs in 
saline solutions, in so far as the tube is gradually and uniformly reduced 
in thickness. The rate of ordinary complete corrosion is too slow to 
be of any serious consequence in practice. Laboratory experiments with 
* Official Summary of report read before the Institute of Metals, 11th March, 1920. 
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