recommendations for spot painting, repainting, or more frequent inspection. The frequency of repainting can be determined by periodic inspection of all coatings. It is important to check on a systematic basis so that painting can be scheduled in advance, at a time when the coating is thin enough, yet has not degraded to the point of disintegration. Thus little surface preparation will be required, and only one or two coats of paint may be necessary.
Paints which are exposed outdoors normally proceed through two stages of deterioration; generally, a change in appearance followed by a gradual degradation. If repainting is not done in time, disintegration of the paint then takes place followed ultimately by deterioration of the substrate (basic surface). Interior coatings generally change slowly in appearance with time but do not usually degrade to any significant extent otherwise.
The first stage of deterioration shows up as a change in appearance of the coating with no significant effect on its protective qualities. This change in appearance may result from soiling, fading, or flattening, depending on the type and color of the paint used and the conditions of exposure.
The second stage of normal deterioration occurs after continued exposure. The coating begins to break down, first at the surface, then, unless repainted, gradually through the coating and down to the substrate. There are two types of degradation that may take place - either chalking or checking and cracking - the degree of either depends on the type of paint and the severity of exposure. When large areas of substrate become exposed, the coating has reached the point of complete deterioration and is in a state of neglect. Such surfaces require extensive and difficult preparation before repainting. All of the old coating may have to be removed for you to ensure that it does not create problems by continuing to lose adhesion, taking the new coating with it. Furthermore, complete priming of the exposed substrate will also be required, thus adding to cost and time. Continued neglect may also lead to deterioration of the structure, resulting in expensive repairs in addition to paint costs.
It is assumed that, through study and experience, you are familiar with the defects resulting from the various stages of deterioration mentioned above and can readily identify them. Therefore, the defects are not described here. 7-20
As with buildings, the maintenance inspection of waterfront structures should be designed to include the following: (1) the prompt detection of deficiencies or damages and (2) the expeditious performance of repairs, consistent with requirements, in an economical and workmanlike manner.
Deterioration of waterfront structures is caused by the destructive forces to which they are exposed, such as the following:
Attack by marine organisms
Rust, corrosion, and decay
Mechanical damage, including the impact and pressure of ships, and the abrasive action of sand and debris
Wave action and erosion
To determine the extent of maintenance and repair work required, an inspection should be made annually of all basic structures (piers, wharves, quay walls, bulkheads, and retaining walls) and semiannually for fenders and movable equipment, such as brows and camels. More frequent inspections than those specified may be necessary under certain circumstances, such as tidal waves, high tides, earthquakes, and action by destructive forces of nature. Inspections may be made from the structures, from a boat or afloat, or from below the waterline by divers. Cameras are often used in visual inspections.
Some of the major defects that can be seen by visual inspection are as follows:
Spans, cracks, and breaks in concrete work.
Rusting of structural steel and exposed reinforcingsteel in concrete.
Decay in wood.
Mechanical damage, resulting in broken or bentstructural members.
Damage by wave action and water erosion, including thewashing out of fill through defective sheetpiling.
Shrinkage of timbers around bolts and cracks aroundloose bolts that allow water to enter. These conditions areusually found in pier curb rails, stringers, wales, pile caps, and other members above the tidal range.
Deterioration of decking.Continue Reading