222 



PAINT TECHNOLOGY AND TESTS 



oxidized condition. Some manufacturers of steel, however, 

 through an understanding of the causes of rust, have progressed 

 in the manufacture of slow rusting materials, either by the 

 elimination, or by the proper distribution of impurities. 



When iron is brought into con- 

 tact with moisture, currents of 

 electricity flow over the surface of 

 the iron between points that are 

 relatively pure and points that 

 contain impurities. These currents 

 stimulate the natural tendency of 

 the iron to go into solution, and 

 the solution proceeds with vigor 

 at the positive points. The air 

 which the water contains oxidizes 

 the iron which has gone into solu- 

 tion, and precipitates the familiar 

 brown iron rust. Thus water, 

 which acts as an acid, and air, 

 which acts as an oxidizer, have 

 combined together to accomplish 

 the downfall of the metal. 



Inhibition and Stimulation of 

 Rust. It is obvious that if means 

 could be devised to stop the solu- 

 tion pressure of iron and make it 

 resistant to the flow of surface 

 electric currents, rust could be 

 prevented. Such methods have 

 been devised, and to better illus- 

 trate how they operate, an analogy 

 may be drawn between iron in 

 water and shellac in alcohol. 



It is common knowledge that 

 when shellac- is placed in alcohol, 

 the shellac will force itself into 

 solution in the alcohol, and form 



Three Photomicrographs of a clear, transparent lacquer. If, 

 Corroding Steel however, there should be mixed 



