IV. Sampling and Sample Preservation 



The most important factor in sampling and sample preservation is to 

 retain, in a useable form, all of the information available from the 

 sample until the information can be extracted. The original location, 

 orientation, and appearance of the sample should be documented. The 

 sample should be removed carefully, properly preserved, and transported 

 to the analyzing facility. 



A. Biological Samples. Most biological samples can be removed 

 from the structure by careful scraping or other means, or they can be 

 removed with the substrate. The samples should then be placed in labeled 

 bottles or jars and covered with ethyl alcohol containing 5% glycerine 



or in a 5% solution of formalin in water. The containers should be well 

 sealed. 



B. Corrosion Products. Samples of corrosion products should be 

 retained for analysis. Sampling should be performed according to 

 Section 3 of the NACE Standard RP-01-73. This standard recommends 

 removal of corrosion products in place on the substrate, if possible. 

 If this is not possible, removal of the corrosion product from the 

 substrate using a nonmetallic or porcelain spatula, or hardened steel 

 pick is recommended. The corrosion product should include any moisture 

 present. The pH of the corrosion product should be determined by 

 placing a short strip of pH-indicator paper on the damp corrosion products 

 (moisten with seawater if necessary) and comparing the resultant color 



of the pH paper with the reference standard furnished with the pH papers. 

 The corrosion products should be collected in individual, labeled, wide- 

 mouth, plastic jars or in plastic bags and sealed to prevent loss of 

 moisture. 



C. Metallic Specimens. Small components should be removed intact ; 

 samples from larger components should be removed by sawing, chiseling, 

 or other method. Flame cutting is undesirable but is often necessary. 

 When flame cutting is used, the sample area should be cooled with wet 

 rags, or other means and left with a 2- to 3-inch margin around the area 

 of interest because the heat of the flame can seriously affect the 

 condition of many samples. Small metal samples can be preserved by 

 placing them in labeled bottles or jars and covering them with n-butanol. 

 Larger samples should be rinsed with fresh water, dried, and sealed in 

 marked plastic bags. 



D. Other Materials. Other materials should be removed so as to 

 minimize damage and preserved according to guidance given by personnel 

 with expertise in their handling. 



E. Transport of Samples. The samples should be packaged in sturdy 

 wooden crates and transported by air freight or rapid surface transport 

 to the analyzing facility. 



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