Metallurgical failure analysis and damage evaluation was requested after extreme hail damaged Galvalume coated steel roofing in Grayson County, Texas. The hail was reported to be 6-8 inches in diameter.
Sections of roofing panels, which exhibited hail damage from light to heavy, were removed for examination. A sampling of hail damage from various roof panels is shown in the photographs below. For size reference, the black insert boxes defining the final sample areas are approximately 3×3 inches.
Photograph A Hail Roofing Damage
Photograph B Extreme hail damage Galvalume roofing.
A scanning electron microscope (SEM) examination of numerous roof samples was conducted. Scanning electron micrographs which are 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 roof sample A2-06 (magnification 50x).
Photograph D Scanning electron micrograph of roof sample A2-07 (magnification 300x).
Photograph E Scanning electron micrograph of roof sample A2-03 (magnification 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 to protect the steel roofing subsurface from concentrated pitting corrosion.