608 BELL SYSTEM TECHNICAL JOURNAL 



the corrosion-fatigue of drill pipe ^* and appears to be an important 

 factor in the retardation of corrosion in certain soils. 



The most extensive soil corrosion test is that which has been carried 

 on under the auspices of the National Bureau of Standards. ^^ In this 

 test, specimens of both ferrous and non-ferrous metals were buried in 

 48 different soils in various parts of the country. Commercial lead and 

 lead containing 1 per cent antimony were placed in these locations and 

 specimens of these have been removed from time to time. These 

 studies have shown that lead and the lead-antimony alloy are corroded 

 by most soils, but at lower rates than are ferrous metals '^ — losses in 

 weight averaging but 10 per cent and depth of pitting about 25 per 

 cent of those shown by the iron and steel specimens. After approxi- 

 mately 10 years exposure in 18 soils the lead-antimony alloy was found 

 in the majority of cases to be slightly but definitely more corroded than 

 was commercial lead. 



A smaller but more intensive soil corrosion test on lead and certain 

 lead-alloys has been carried on by the Bell Telephone Laboratories in 

 five typical soils in the general vicinities of Lafayette and Monon, 

 Indiana. Three grades of lead * and alloys of these leads with an- 

 timony in amounts from 0.8 per cent to 2.5 per cent and with 3 per cent 

 tin were chosen for this test. The specimens consisted of fiat plates 

 one square decimeter in area prepared from metal which had been 

 extruded in the form of tape. Before burial these plates were de- 

 greased with carbon tetrachloride and scoured with fine sea sand. 

 Five specimens of each material were buried at each location in a 

 horizontal position at a depth of two feet. After a period of four 

 years the specimens were removed from the soil, and after removal 

 of the corrosion products, the losses of weight and the maximum depth 

 of pitting determined. 



The values for loss of weight are represented graphically in Fig. 1, 

 in which all of the metallic materials are compared in each of the soils. 

 The arithmetical averages are shown in all cases by means of broken 

 lines. The maximum depth of pitting results showed a close corre- 

 spondence to the losses of weight. For example, it was least in the 

 Plainfield fine sand and the Fox silt loam and greatest in the Miami 

 silt loam. The only specimens perforated by pitting were the lead-tin 

 alloy and these only in the last mentioned soil. 



* The grades of lead employed in this test and in the sulfation tests described later 

 in this paper are designated as: Corroding or A.S.T.M. Grade I, 99.94 per cent 

 lead; Chemical or A.S.T.M. Grade II, 99.90 per cent lead; and Common or A.S.T.M. 

 Grade III, 99.85 lead. The principal impurity in chemical lead is copper, and in 

 common lead, bismuth. The term "corroding" applied to the high purity product 

 arose in connection with its use in the manufacture of white lead; it does not imply 

 greater corrodibility. 



