Internal superstructure area

The painting areas of a ship are shown in Figure 11.1. The main requirement of marine coating systems is corrosion prevention. Detailed requirements vary with the particular internal or external area (e.g., chemical resistance in cargo tanks resistance to seawater in ballast spaces heat resistance in engine rooms impact and abrasion resistance on boottoppings, external hulls, and decks cosmetic qualities on superstructure and topsides). 

Rotational, translational, and mirrored domains are prevalent in the presence of adsorbate superstructure or adsorbate-induced reconstruction. A surface structure with symmetry lower than the symmetry of the substrate can produce such domains by applying all symmetry operations of the substrate. Since different domains with the same internal structure have the same structural energy, these domains should have an equal existence probability on a surface. If the areas of any domains presented on the surface are larger than the lateral coherence length of the incident electron beam, which is typically in the order of few tenths of a nanometer, the LEED pattern becomes the sum of the individual diffraction patterns of each domain. However, in cases where the symmetry of the surface is distorted by steps or by a strain, it is possible to eliminate certain domains selectively and one domain becomes dominant. Figure 7A shows an example of a well-oriented surface that contains three rotational domains, and Figure 7B displays a one-domain sample obtained using a stepped surface. 

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