Evaluation of Test Specimens 



After the test specimens were recovered from the sea, they were 

 examined visually for gross corrosion damage and fouling attachment. The 

 corrosion products and the attached fouling organisms were then removed 

 from the test specimens as described under "Preparation of Test Specimens." 

 The panels were processed twice through the chemical cleaning procedure 

 and the final weight change determined and recorded. The weight loss due 

 to chemical cleaning on control panels was also determined and taken into 

 account during final evaluation of marine corrosion. The weight losses due 

 to corrosion are expressed in milligrams lost per square decimeter of exposed 

 surface per day (mdd). This unit was converted to indicate depth of penetra- 

 tion as mils per year (mpy). 



RESULTS AND DISCUSSION 

 Shallow-Water Tests 



Exposure Test No. 1 (70, 1 12, and 268 Days). The carbon steel and 

 aluminum alloy test panels were exposed in the sea beginning in the month 

 of January in two ways as follows; (1) placed inside cylindrical test chambers 

 sealed with membrane filters (control panels), and (2) placed on phenolic 

 plastic strips (exposed panels). 



When the panels were recovered after 70 days in the sea, the exposed 

 steel and aluminum alloy panels were covered primarily with a light growth 

 of Ectocarpus (brown algae), hydroids, and corrosion products (Figure 6). 

 The control panels were free of any marine growth. However, the surfaces of 

 these control steel panels were covered uniformly with a fine, powder-like 

 red rust (Figure 7). A small amount of white corrosion products had formed 

 over the edges and ends of control aluminum alloy panels; however, the sur- 

 faces were relatively free of such corrosion products (Figure 8). The condition 

 of the exposed and control panels after undergoing chemical cleaning is shown 

 in Figures 9 through 13. The surfaces of exposed steel panels were irregular 

 (rough), while the surfaces of the control panels were relatively smooth. The 

 exposed aluminum alloy panels had numerous shallow and deep pits over their 

 surfaces. Severe corrosion had also occurred along the edges and ends of these 

 panels. On the other hand, the control aluminum alloy panels were free of 

 surface corrosion or pittings, but minute corrosion did occur along the edges 

 and ends of these panels. 



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