Peeling Back the Layers on Corrosivity

Author: ACTenviro Corporate
Date: February 3, 2024

In “Understanding the Four Characteristics of Hazardous Waste,” we covered the first step in managing your hazardous waste: determining if it is, in fact, a waste, as defined by the EPA. Suppose your waste for example does not appear on one of the EPA’s four lists of hazardous wastes; your next step is to see if it exhibits any of the four characteristics established by the Resource Conservation and Recovery Act (RCRA): ignitability, corrosivity, reactivity and toxicity. Additionally, some states, including California and Washington, have their own state-specific requirements that expand on the RCRA definitions.

Corrosive materials can attack and destroy tissue or metal. The EPA definition of “corrosive” waste is found in 40 CFR 261.22, is based on the pH of liquid wastes — acids have low pH, while bases or “caustic” liquids have high pH — and includes the following:

  • Aqueous waste liquids (wastes with at least 20% water by volume) with a pH of less than 2 or greater than 12
  • Any waste liquids that corrode steel at a rate greater than a quarter-inch per year


This definition only applies to aqueous liquids. It does not apply to solids (or non-aqueous liquids), and the EPA does not recognize “corrosive solids” as a type of hazardous waste. However, California regulations (22 CCR 66261.22) do include a definition of “corrosive solid.” This means California generators with waste that would have a pH of less than or equal to 2, or greater than or equal to 12.5 when mixed with an equivalent weight of water must manage those wastes as non-RCRA hazardous waste corrosive solids.

The EPA manual of test methods, SW-846, has specific tests for various hazardous waste properties and parameters, including corrosivity. SW-846 references test method 9040 to measure pH for hazardous waste characterization. The test method requires samples to be analyzed “as soon as possible,” because the pH of some samples can change over time. While not strictly applicable to hazardous waste determination, additional guidance from the EPA (in 40 CFR 136.3, table II) requires pH samples to be analyzed within 15 minutes of collection to ensure accuracy.

Since it is not practical to submit samples to a lab for analysis within 15 minutes of sample collection, many generators choose to rely on “generator knowledge” of their wastes to evaluate corrosivity. This is often supplemented by field methods to measure pH, such as using pH paper or electronic pH meters.

Examples of corrosive wastes include hydrochloric or sulfuric acid and sodium hydroxide solutions. Wastes that are determined to be corrosive based on RCRA definitions are assigned the EPA hazardous waste code D002. EPA hazardous waste codes do not apply to non-RCRA hazardous wastes, such as corrosive solid waste in California. However, there may be state codes that do apply.

ACTenviro can assist generators in making determinations for their potentially hazardous wastes. If you have any questions about hazardous waste — from classification to management to disposal — please e-mail us at [email protected]. We’re happy to help!

James Kapin is Principal Advisor for safety, health and environmental compliance for ACTenviro.  Jim is a Certified Industrial Hygienist (CIH) and a Certified Safety Professional (CSP) with over 25 years of workplace safety and environmental protection experience.   Do you have any hazardous waste questions for Jim?  Or any other workplace safety or environmental compliance questions?  Let us know at [email protected]


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