Sulfuric acid modification of CCA treating solution is often used to control the formation of sludges and undesirable deposits on the surface of treated wood. The consequences of sulfuric acid addition are examined in this work and negative effects are shown to far outweigh any benefits. Major risks include the loss of copper due to leaching from treated wood and the accelerated corrosion of treating equipment when even small quantities of sulfuric acid are employed. Twenty-year stake test results demonstrate that the addition of as little as 0.5% by weight of sulfuric acid to CCA treating solution can result in premature field failure. A mechanism for the effects of sulfuric acid on the chemistry of this system is discussed.

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