With these photographs, it was possible to determine the site density, the average filament length, the corrosion number, and the area of corrosion.
corrosion number = site density x average filament length (1)
In addition to the corrosion number, the area of corrosion along the matrix scribe and around the fastener was also determined using the image analysis software, Image Pro Plus.
The corrosion number at 1000 hr for the different treatments is displayed in Table 3, and was obtained using equation (1) and the initial site density.
As an alternative to the corrosion number, the growth in corrosion area was also examined.
(40) The greater sensitivity of the area is probably due to the inclusion of the corrosion front from the scribe (only the length of the 10 longest filaments is measured for the average length or corrosion number) and/or the width of the filaments.