The weld beads on Ni-Cr-Fe 718 alloy made from 718 electrodes were 

 uncorroded. 



The weld beads on Ni-Cr-Fe X750 alloy made from electrodes 69 and 

 718 were selectively corroded during exposure at the surface and at 

 the 2,500-foot depth, except the bead made from electrode 69 at the 

 2,500-foot depth. 



The weld beads on Ni-Cr-Mo 625 alloy made with 625 electrodes were 

 uncorroded. 



The weld beads on Ni-Fe-Cr 800 alloy made with electrodes 82 and 

 138 were selectively attacked during exposure at the surface and at the 

 2,500-foot depth. 



The weld beads on Ni-Fe-Cr 825 alloy made with electrode 135 were 

 selectively attacked while weld beads made with electrode 65 were un- 

 attacked at the 2,500-foot depth and only by incipient pitting at the 

 surface. 



STEELS 



The chemical compositions of the steels are given in Table 8 and 

 their corrosion rates and types of corrosion in Table 9. The effects 

 of depth, concentration of oxygen in seawater and time are shown graphi- 

 cally in Figures 20 to 22. 



Since the corrosion rates of the steels were nearly the same at 

 any one depth, the average values for any one depth were averaged and 

 plotted in Figures 20 to 22. 



The effect of depth on the average corrosion rate of the steels is 

 shown in Figure 20 . The variation of the concentration of oxygen in 

 seawater with depth is also plotted in Figure 20 for comparison purposes. 

 The shapes of the curves for the steels and AISI 1010 steel show that 

 the corrosion rates are not depth (pressure) dependent. The shapes of 

 those curves are practically the same as the shape of the oxygen curve, 

 indicating that the concentration of oxygen exerts a major influence on 

 the corrosion of steels in seawater. 



The effect of the concentration of oxygen in seawater on the corro- 

 sion rates of steels is shown in Figure 21. The curve for the average 

 corrosion rates of all the steels is a straight line, indicating that 

 the corrosion rates of steels in seawater are proportional to the oxy- 

 gen concentration. 



The corrosion rate of AISI 1010 steel and the averages of the cor- 

 rosion rates of all the carbon and low alloy steels after one year of 

 exposure versus the oxygen content and the temperature of seawater were 

 analyzed using the technique of linear regression analysis. By this 

 technique a relationship between oxygen content, temperature and cor- 

 rosion rate was obtained for both the average of all carbon and low 

 alloy steels and for AISI 1010 steel. The derived formulae are: 



