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Q&A: How do I Determine If I Have a Class 8 Corrosive per USDOT/PHMSA Regulations?

Q&A: How do I Determine If I Have a Class 8 Corrosive per USDOT/PHMSA Regulations?

This conversation started with a phone call in late May 2016:

In sum, a business was trying to determine the information necessary in order to classify a substance as a Class 8 Corrosive for transportation in commerce.  He had been told that the classification is based on the pH of the substance.  I told him that I was almost certain that pH was not a factor in this classification but instead was based on the corrosion rate of the substance on human skin or on steel or aluminum.  Not having a copy of the Hazardous Material Regulations with me at the time I took the call I couldn’t cite the regulation my answer was based on so I told him I would follow-up with an email.

And so I did.  In an email of May 31, 2016:

My first answer was correct that the USDOT definition of a Class 8 Corrosive Material (liquid or solid) at 49 CFR 173.136 is not based on and does not refer to the pH.  Whether a material is a Class 8 is based on two criteria:

  • If it causes full thickness destruction of human skin at the site of contact within a specified period of time (see 49 CFR 173.137).


  • If it has a severe corrosion rate on steel or aluminum (see 49 CFR 173.137).
“Whenever practical, in vitro test methods authorized in 173.137 of this part or historical data authorized in paragraph (c) of this section should be used to determine whether a material is corrosive.”
I hope this helps.

He was pleased and had a question I couldn’t answer:

Very helpful!  THX
Do you know where/who can perform these tests for our blend?   Is it up to the manufacture?
… I have been in and around DOT regs for 15 years and wasn’t clear on this one
I’ll certainly keep you in mind.

I accepted the compliment but deflected the question:

You’re welcome.
I am not aware of a lab that performs the necessary analysis.  I think if you Google the requirements and reference the regulations you should find one.