26 



Combination Eods. 



There are rods on the market made of a sheath of copper surrounding iron or 

 steel centre. All these are even less durable than if made of iron alone, because- 

 of electrolytic action between the two metals and rapid rusting either with or with- 

 out this action. Different farmers who have had rods of this style on their buildings 

 and have examined the groundings from time to time have told us that in their 

 experience with rods having copper sheath and strip of iron or steel in the centre, 

 sometimes with two steel wires added for strength, the life of the iron has proved 

 to be from ten to twelve years. On the 3rd of February, 1914, the writer person- 

 ally inspected one of these rods that had been on a building eight years and found 

 that in the portion of the cable running along the ridge of the barn the iron strip 

 and the steel wires were almost completely destroyed by rust, in spite of the fact 

 that both strip and wires had once been galvanized! Fig. 34 shows the result 

 better than words. 



a b c d 



Figure 34. — The story of a copper-covered rod. 



a. The new rod complete. 



b. The new rod torn to pieces. Note the copper sheath, two No. 10 galvanized 



steel (iron) wires, and %-inch strip of No. 20 galvanized iron. * 



c. All that was left of a rod that had been in use eight years. The sheath in 



good condition, but the steel wires and strip nearly all rusted away. 



d. The rust taken from the sample one foot long shown in c. 



The portions of the rods running up the gable ends were in fair state of 

 preservation. The ground-rods were frozen in so that their condition could not be 

 determined. One could hardly have anticipated such destruction up on the ridge 

 of the barn, but the explanation is easy. During rains the water entered the 

 sheath, wetting the iron, and after the storms the rods became heated, and mois- 

 ture and warmth combined produce most rapid rusting, a phenomenon with which 

 all are familiar. In much less than eight years the iron in those rods ceased to 

 have any value, so far as that portion along the ridge was concerned. And it would 

 seem impossible that the iron in the ground-connections, subject to perpetual mois- 

 ture, could have escaped the effects of rust. 



In the country great quantities of this type of rod have been used. What 

 percentage of it has become defective we have no means of knowing. Of course, 

 so long as the copper sheath remains intact there is protection, because the chief 



