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Steel
Roof Hail Damage
Metallurgical failure analysis and
damage evaluation was requested after extreme hail
(hailstones 6-8 inches in diameter) damaged
Galvalume coated steel roofing in Grayson County, Texas.
Sections of roofing panels, which exhibited damage from light to heavy,
were removed for examination.
A sampling of hail damage from various roof panels
is shown in the photographs below. The black insert
boxes, defining the final sample areas, are
approximately 3 inches along each side.
Photograph Set A
Photograph Set B
A scanning electron microscope (SEM) examination
of numerous roof samples was conducted. Scanning
electron micrographs (photographs from the scanning
electron microscope) of the sample denoted A2 at
magnifications of 50x and 300x are shown in the
photographs below.
Photograph C: Scanning
electron micrograph of sample A2-06 at an original
magnification of 50x.
Photograph D: Scanning
electron micrograph of sample A2-07 at an original
magnification of 300x.
Energy dispersive spectroscopy (EDS), which is
chemical analysis within a defined area, was conducted
within the box denoted in the photograph below
Photograph E: Scanning
electron micrograph of sample A2-03 at an original
magnification of 1,000x.
The
chemical analysis within the crack revealed a
large concentration of iron (Fe). These results indicated that
the cracks resulting from the extreme hail had penetrated the
Galvalume steel coating to the steel substructure.
The effect of the cracking in the Galvalume roof
coating will be unknown until sufficient time has
elapsed to determine if the cracked Galvalume
surface had enough chemical activity, i.e., galvanic
throwing power, to protect the
steel roofing subsurface from concentrated pitting
corrosion.
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Dr.
R. Craig Jerner, Ph.D., PE specializes in accident
investigation and metallurgical failure analysis,
with over 30 years experience as a metallurgical
consultant and accident investigator. He has
testified as a metallurgical expert in over 250
depositions and more than 70 court appearances. If you or someone you know should need the services of Dr. Jerner and J.E.I. Metallurgical, please visit our web site at the buttons below, or e-mail Dr. Jerner --- 