ENVIRON research team answers critical question about corrosion from Chinese drywall

Date: April 16, 2012

The nature of corrosion resulting from corrosive gypsum wallboard (Chinese drywall)—and its progression after removal of the gypsum source—has been demonstrated through a series of experiments undertaken by ENVIRON scientists in collaboration with a group of metallurgists and materials scientists.

Continued corrosion after removal of corrosive drywall, co-authored by Principal Robert DeMott and Senior Science Advisor Thomas Gauthier, and published in the June 2011 edition of the Journal of Failure Analysis and Prevention, reports on results obtained through ENVIRON’s collaboration with metallurgists and materials scientists directly assessing the progressive nature of corrosive reactions resulting from sulfur-containing compounds released from corrosive gypsum wallboard.

Their research pertains to the nature of corrosion occurring on copper affected by reduced sulfur gases from corrosive gypsum wallboard. Previous studies on the effects of this wallboard had observed that the morphology of the corroded layer—and the pitting observed beneath a layer of corrosion residue—suggested an atypical form of corrosion on copper that could progress via reactions with the residue itself, even if the source of reduced sulfur gases was removed. This would have major potential implications regarding repairs for structures with corrosive wallboard—removing the wallboard might not be sufficient to halt the corrosion process.

Testing this possibility, the ENVIRON team and their collaborators designed a prospective study to directly test whether corrosion initiated by corrosive wallboard could then progress without the continued presence of the wallboard. Using a series of experiments in which wallboard was removed after a certain period and new copper was placed in contact with corroded copper, they were able to demonstrate the occurrence of progressive corrosion in the absence of wallboard.

Continued corrosion after removal of corrosive drywall is the first report specifically demonstrating that the corrosive process initiated by corrosive gypsum wallboard can continue even after the wallboard is removed. While the specific mechanisms of the progressing corrosion require further investigation, implications for repairs relating to corrosive wallboard are clear. Materials already corroded by the wallboard could continue to corrode if left in place when the wallboard is removed. This finding has important ramifications to owners and parties involved in repairs.

For more information, contact Robert DeMott.