Understanding Gypsum Wallboard as a Source of Corrosive Effects on Building

Components

James L. Poole, Ph.D., CIH

ENVIRON International CorporationTampa, FLjpoole@environcorp.com

Overview

Linking observed corrosive effects to wallboard

Constraints imposed by the materials and unique chemistry

Reproducibility of corrosion effects

Misconceptions and alternate theories

Reality 1 – Ongoing Production

Corrosive gas production is an ONGOING Process

- NOT simply release of stored gas from production

- Chemical reactions will continue for many years

HVAC Coil Tubing Analyzed

Tubing was cut off, surface scale analyzed, then removed to visualize underlying surface.

Micrograph after removal of black corrosion scale showing pitting penetrating into the surface of the coil tubing

Coil Analysis ConclusionsX-ray spectroscopy

documents scale is sulfur-based, not oxidative (green) corrosion common on copper.

Pitting corrosion - is progressive beneath scale

unless this is entirely removed.

- leads to perforation, failure of coil.

Electron micrograph showing corrosion-pitted external

surface of coil

Pitting Corrosion Found on Plumbing

Stub-out for water supply to vanity Electron micrograph of exterior surface showing aggressive corrosion

Reproduction of Corrosion

To link “suspect” Chinese manufactured drywall with observed corrosive effects, samples of domestic and Chinese wallboard were obtained for a real-time evaluation under ambient conditions

Identically sized samples of each type (domestic and Chinese) were prepared and placed in sealed study chambers

Chamber Test of Sulfide Gas Emissions & Corrosion Potential

Chinese and domestic wallboard placed in sealed jars with:- new, clean, polished copper

plumbing pipe; and

- moist sponge (humidity source).

Gases sampled at week 18.

Reduced Sulfur Gases Found

Laboratory analysis (ASTM D-5504) showed elevated levels of carbonyl sulfide and carbon disulfide in chambers with Chinese wallboard

Carbonyl Sulfide(μg/cm2)

Carbon Disulfide(μg/cm2)

Chinese(n=4)

228 249

Domestic(n=2)

26 58

Copper Matches Reduced Sulfur Effects

Pipe from Chamber w/ Chinese Wallboard

Copper Pipe from Chamber w/ Domestic

Wallboard

Microscopic & Chemical Analysis of Chamber Samples Matches Effects on HVAC Coils

Sulfur corrosion identical to that on HVAC coil was found only on pipe from foreign wallboard chamber.

Pitting on pipe from foreign test chamberUndamaged pipe from domestic test chamber

Corrosion Will Not Stop

Corrosion process occurring on copper is progressive- Removing source of gases is insufficient

- Existing corrosion layer will feed further corrosion

- Pitting will inevitably create leak or failure

- Remedy must remove corrosion layer

Misconception 1Beware of Fool’s Gold

Mineral iron pyrite (Fool’s gold) initially suggested as source of gases

Present at same levels in bad imported board and good domestic board

Assuming iron pyrite is the mechanism will lead to false implications of non-defective (US) products

Misconception 2Wallboard Made from Hazardous or Radioactive Waste

Coal ash, fly ash and slag are misnomers which result in unfounded fears

Wallboard is not a phosphogypsum product; nor does it contain unusual radioactivity!

Gypsum can be made synthetically when gases are passed through limestone

Misconception 2 (continued) Minerals Tell the Tale

Minerals found in foreign wallboard are incompatible with gypsum produced synthetically:- Elemental sulfur (which cannot survive burning)

- Iron pyrite, other geological trace metals

The presence of these minerals confirms that defective board is mined gypsumThis has been further supported by the identification of specific mines in China Involved in the production of the wallboard of interest as reported in the media

Misconception 3Sulfuric Acid

Conversion to sulfuric acid theorized as causing corrosion- Recognized from acid rain reactions

- Occurs in the atmosphere via ozone, strong “free radicals”

- Limited Indoor Potential (requires strong oxidizers)

Alternate TheoryWater Damage and Microbes Hypothesis

Common source of sulfide gases is certain bacteria:- Sulfate-reducing bacteria

- Carry out reduction reactions only in the ABSENCE of airborne oxygen -- “down in the swamp”

- These are anaerobic processes

Confounding Variables with Bacteria Theories

Non-water damaged affected foreign wall board produces these reduced sulfur gases- In ROOM AIR

- with ambient air and more specifically in the presence of oxygen (not anaerobic conditions)

- Reduced Sulfur Gas production continues AFTER sterilization and results in continued corrosion of copper

Defective wallboard produces reduced sulfur gases through

CHEMICALnot BIOLOGICAL

processes

Closing CommentsReduced sulfur gases are produced by

affected foreign wallboard

These gases result in corrosion

These effects are reproducible and differentiate domestic wallboard from affected foreign wallboard

Unique chemistry – Determines Effects and Constrains Explanations

Closing Comments

The goal of the symposium is the presentation of relevant, sound technical information as opposed to armchair theories

Thank You!