CHAPTER XVI 

 STRUCTURAL STEEL PAINT TESTS 



The Necessity of Protective Coatings. Most painters have 

 in the past considered of minor importance the painting of iron 

 and steel; any paint that would properly hide the surface of the 

 metal being accepted without much question. The demand, 

 however, for structural steel for office buildings, factories, steel 

 cars, railroad equipment, etc., has doubled the output of struc- 

 tural paints, and created a demand for painters having a knowl- 

 edge of the proper materials to use in the painting of steel, so 

 that its life may be preserved, and its strength maintained. 

 Such knowledge is as important to the painter as a knowledge 

 of how to properly select materials for the painting of wood, and 

 how to temper these materials to suit the various conditions met 

 with. 



The Cause of Rust. Everyone is familiar with the appearance 

 of rust, but few actually understand what causes rust. No 

 attempt will be made here to present even an outline of the many 

 theories advanced to explain the phenomenon of the rusting of 

 iron, for the subject is. as diverse as it is interesting. A brief 

 resume, however, will be given of the now generally accepted 

 theory that explains the subject. This theory is called the elec- 

 trolytic theory. " Auto-electrolysis " is the term used to define 

 the peculiar tendency of iron to be transformed from a metal 

 possessing a hard lustrous surface, high tensile strength, and 

 other useful properties, to a crumbling oxide that falls to the 

 ground and again becomes part of the earth from which it was 

 originally taken by man. 



This " going back to nature " is more readily accomplished 

 by most of the steel produced to-day than by the old hand-made 

 irons produced many years ago. It seems to be a curious fact 

 that the more quickly a product or an article is fashioned by 

 man, the more quickly it tends to return again to its original 



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