226 PAINT TECHNOLOGY AND TESTS 



acids stimulate the corrosion of iron, it was suggested that the 

 action of more or less pure pigments on iron in the presence of 

 water should be thoroughly investigated. Two years ago this 

 Committee invited the co-operation of Committee D-l (then 

 known as Committee E) in the investigation, and a special sub- 

 committee representing the two main committees was appointed. 



" The methods and results of the water-pigment tests have 

 previously been reported and published, and need not be given 

 in detail. Briefly, the method consisted in immersing samples 

 of steel in water suspensions of the various pigments and blowing 

 air through the containers for definite periods of time, the corro- 

 sion being measured by the loss in weight sustained by the test 

 pieces. About fifty pigments which are in more or less common 

 use for painting steel were purchased in the open market and dis- 

 tributed among a number of the members of the Committee, 

 who agreed to carry out the work. Each investigator worked 

 independently of the others, except that the same general method 

 was followed; the time of exposure to the corroding action, 

 however, varied in the different experiments. When the results 

 were compared and analyzed by the sub-committee, it was felt 

 that the general agreement of the results obtained by the several 

 investigators was striking and merited further and more system- 

 atic work. As a result of these tests the sub-committee ten- 

 tatively divided the pigments into inhibitors, stimulators, 

 and indeterminates. The word ' indeterminate ' was selected 

 after considerable discussion, because the words ' neutral ' 

 or l inert' already possess a special meaning as applied to paint 

 technology. The Committee takes this occasion to emphati- 

 cally state that in adopting this tentative classification, the words 

 1 inhibitive ' and ' stimulative ' as used by them up to the 

 present time apply only to the results obtained in the water tests, 

 and the inference that the results obtained have decided which 

 class the pigment will fall into when made into a paint with the 

 usual vehicles and used as a protective coating on iron and steel, 

 is not justified. In order to make this point quite clear, it has 

 been agreed by the Committee to qualify the classification so 

 as to speak of the various materials tested as ' water stimulative' 

 or ' water inhibitive.' ' 



Importance of Field Tests. Although the laboratory accel- 

 erated tests for the determination of the relative value of struc- 



