Chemical Plant Workers Fall From Unsafe Catwalk

Case Overview

This case involves two workers who fatally fell from scaffolding at a chemical plant after the catwalk collapsed. The scaffolding at this plant was made out of zinc and located near tanks that emitted hydrogen sulfide. An expert in corrosion engineering was sought to discuss corrosion hazards associated with wastewater treatment and determine if facility conditions had caused the zinc to rust.

Questions to the Materials expert and their responses

Please describe your experience in corrosion engineering.

I have been engaged in corrosion research for 43 years and served as a consultant on corrosion-related failures for 32 years. A significant portion of my work involves corrosion associated with wastewater.

What corrosion hazards do chemicals / microbes cause?

The specific hazards depend on the specific chemicals. Hydrogen sulfide reacts strongly with iron (e.g., carbon steels and low alloy steels) and generates a solid corrosion product film that might slow down subsequent corrosion. However, the solid sulfide film is often non-protective for several reasons, resulting in significant corrosion of the steel. Zinc is also susceptible to corrosion by hydrogen sulfide. Both iron and zinc typically suffer significant corrosion when exposed to sulfuric acid.

How are corrosion hazards in facilities mitigated?

Mitigation techniques include: control of oxidizers (such as dissolved oxygen and chlorine); adjustment of pH; addition of organic inhibitors; cathodic protection; electrically insulating coatings (e.g., polymers); sacrificial anodes.

About the expert

This highly qualified expert has a BS, MS, and PhD in Metallurgy from the Massachusetts Institute of Technology. He was a staff scientist for 11 years at General Electric?s Corporate Research and Development Center. He served as Chairman of the Department of Materials Science and Engineering at the University of California, Berkeley. He has authored over 80 technical publications and has 22 patents. His work has been recognized with several awards including the Joseph Vilella Award of the American Society for Testing and Materials, and the Alfred H. Geisler Award of the American Society for Metals. This expert is currently a Professor at a university in California and his research interests heavily focuses on understanding and improving the corrosion resistance of materials.