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The formation of pits; in the fingernails, a consequence and sign of psoriasis.
The preservation for a short time of indentations on the skin made by pressing with the finger; seen in pitting edema.
Selective localized formation of rounded cavities in a metal surface due to corrosion or to nonuniform electroplating.
(mining engineering)
The act of digging or sinking a pit.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

popping, blowing, pitting, pops

Shallow conical depressions, ranging in size from pinheads to diameters of ¼ in. (64 mm), just below the surface of a lime-putty finish coat; caused by the expansion of coarse particles of unhydrated lime or of foreign substances.


1. The development of small cavities in a surface, owing to phenomena such as corrosion, cavitation, or (as in concrete) localized dis-integration.
2. In plastering, See popping.
3. The development of localized surface defects on a metal surface, e.g., small depressions, usually caused by electrochemical corrosion.
4. The localized corrosion in the form of cavities which takes place on the surface of a metal.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

compressor blade damage

compressor blade damageclick for a larger image
Various types of damages that compressor blades can sustain. Only one or two may take place simultaneously though these have been combined in this illustration.
The various types of damages to compressor blades and their appearances are as follows:
i. Bend. The blade gives the appearance of ragged edges. Smooth repair of the edges or surface in question can be carried out, but the extent of the damage that can be repaired is limited.
ii. Bow. The main source of this type of damage is a foreign object. The blade is bent at the tips and the edges.
iii. Burning. The damage is caused by overheating. The surface of the blade is discolored. If the overheating is severe, there may be some flow of material as well.
iv. Burr. A ragged or turn-out edge is indicative of this type of damage. This takes place during the grinding or cutting operation of the blade at the manufacturing stage.
v. Corrosion. Oxidants and corrosive agents, especially moisture present in the atmosphere, are the main reasons for the corrosion or pitting of the blades. Normally, regular washing is sufficient to prevent it. The blade gives a pitted appearance, and there is some breakdown of the surface of the blade. Also called pitting.
vi. Cracks. Excessive stress from shocks, overloading, or faulty processing of blades during manufacturing can cause cracks and result in their fracture.
vii. Dent. These can be caused by FOD (foreign-object damage) or strikes by dull objects like those in bird strikes. Minor dents can be repaired.
viii. Gall. This type of damage is from the severe rubbing of blades, in which a transfer of metal from one surface to another takes place.
ix. Gouging. The blade gives the appearance of displacing material from its surface, and a tearing effect is prominently visible. This type of damage is from the presence of a comparatively large cutting material or foreign body between moving parts.
x. Growth. The damage manifests itself in the form of elongation of the blades. Growth type of damage takes place because of continued and/or excessive heat and centrifugal force.
xi. Score. Deep scratches are indicative of scoring, which is caused by the presence of chips between surfaces.
xii. Scratch. Narrow and shallow scratches are caused by sand or fine foreign particles as well as by mishandling the blades.
xiii. Pitting. Pitting takes place because of atmospheric corrosion, especially seawater. The surface of the blade shows signs of pitting.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved