breezy days. The painting method requiring the mosttraining is spraying. Rolling requires the least training.PAINT FAILURESLEARNING OBJECTIVE: Upon completing thissection, you should be able to identify thecommon types of coating failures and recognizethe reasons for each.A coating that prematurely reaches the end of itsuseful life is said to have failed. Even protective coatingsproperly selected and applied on well-prepared surfacesgradually deteriorate and eventually fail. The speed ofdeterioration under such conditions is less than whenimproper painting procedures are earned out. Inspectorsand personnel responsible for maintenance painting mustrecognize signs of deterioration to establish an effectiveand efficient system of inspection and programmedpainting. Repainting at the proper time avoids theproblems resulting from painting either too soon or toolate. Applying coatings ahead of schedule is costly andeventually results in a heavy buildup that tends toquicken deterioration of the coating. Applying a coatingafter it is scheduled results in costly surface preparationand may be responsible for damage to the structure,which may then require expensive repairs.In the following sections, we’ll look at some of the morecommon types of paint failures, the reasons for suchfailures, methods of prevention, and cures.SURFACE PREPARATION FAULTSPaint failures can result from many causes. Here, we’lllook at some of the most common caused by faults insurface preparation.AlligatoringAlligatoring (fig. 8-3) refers to a coating pattern thatlooks like the hide of an alligator. It is caused by unevenexpansion and contraction of the undercoat. Alligatoringcan have several causes: applying an enamel over an oilprimer; painting over bituminous paint, asphalt, pitch, orshellac; and painting over grease or wax.PeelingPeeling (fig. 8-4) results from inadequate bonding ofthe topcoat with the undercoat or the underlying surface.It is nearly always caused by inadequate surfacepreparation. A topcoat peels when applied to a wet, dirty,oily or waxy, or glossy surface. All glossy surfaces mustFigure 8-3.—Alligatoring.Figure 8-4.—Peeling.be sanded before painting. Also, the use of incompatiblepaints can cause the loss of adhesion. The stresses in thehardening film can then cause the two coatings toseparate and the topcoat to flake and peel.BlisteringBlistering is caused by the development of gas or liquidpressure under the paint. Examples are shown8-11
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