Application

Figure 2-24. Cracked Aluminum Panel Comparing Results with an Optimum Thickness Layer (Top) to an Excessive Layer (Bottom) of Developer

Nonaqueous Solvent Suspended Developers.

TM-1-1500-335-23 Nondestructive Inspection Methods Manual
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T.O. 33B-1-1 2-68 2.6.5.3 Application. CAUTION Water soluble developers SHALL NOT be used on parts processed with water washable, Method A, fluorescent penetrants or any visible-dye penetrants, unless specifically authorized NOTE Wet, soluble developer in open immersion tanks is subject to evaporation. As the water evaporates, the developer concentration increases. A solution concentration level should be established and maintained by the addition of water and dry powder. The developer may be applied by spraying, flowing, or immersion. If the immersion process is used, the part should not remain in the solution any longer than required to provide complete coverage. The developer may be applied to parts while they are still wet from the water wash after penetrant removal. Care must be exercised to prevent entrapment of soluble developer in the part cavities or concave surfaces (pooling). The developer should wet the part surface with no water break areas after application. After the developer is applied, the parts must be oven dried, since room temperature evaporation is too slow. The developing action does not start until the developer is dry. 2.6.5.4 Advantages. a. The primary advantage of water soluble compared to water suspended developer is the elimination of the need for agitation to keep the particles in suspension. b. The coating does not produce streaks or runs that often occur with wet suspended developers. c. The developer particles, being soluble in water, are very easy to remove during postcleaning. 2.6.5.5 Disadvantages. NOTE Water soluble developers are subject to bacterial growth. The susceptibility is dependent on the geographical area and the type of local water. The first indication can be a foul odor or visible growth. a. Water soluble developers contain wetting agents that can act as penetrant removers and must be carefully used. This removal action is accelerated with water washable penetrants. Therefore, water soluble developers SHALL NOT be used on parts processed with water washable penetrant. b. Even though a thick, white coating is produced, water soluble developers do not function well with visible-dye penetrants. Water soluble developer SHALL NOT be used with visible-dye penetrants. c. Like the wet suspendible developers, the biocides in water soluble developers only delay bacterial growth. The water soluble developers must be discarded when bacterial growth is noticed and the tank or container completely disinfected prior to mixing a new solution.

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