ADR legislation ensures the safe transport of dangerous substances

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The European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR) contains a set of rules that must be followed to transport dangerous chemical substances. In this article we’ll discuss the different classifications pertaining to the ADR legislation. 

Classification of chemical substances

Chemical substances that are regarded as dangerous goods are divided into different classes. 

Class 8 are the so-called corrosive substances: substances that by chemical action can affect the epithelial tissue of the skin with which they come into contact or that can affect other goods or means of transport. According to their corrosiveness, these chemicals are subdivided into three groups:

  • Packing group I: Substances presenting high corrosivity
  • Packing group II: Corrosive substances
  • Packing group III: Slightly corrosive substances

The following applies to substances in group III (mildly corrosive substances):

  • There is either a slight interaction with the skin (destroys intact skin tissue over the full thickness of the skin over a period of up to 14 days, starting from an exposure time of minimum 60 minutes to maximum 4 hours);
  • Or there is no damage over the entire thickness of the skin but a corrosion rate of more than 6.25 mm/year is observed by means of a corrosion test on aluminum and carbon steel.

Based on the result of the corrosion test, it can be assessed whether a substance belongs in class 8 - packaging group III or rather in another class. This is done by testing the corrosivity of the chemicals on carbon steel/aluminium. 

More information on the corrosion test can be found below.

How is an ADR corrosion test performed according to ADR legislation?

The test is described in Section 37.4, Part III of the UN Recommendations on the Transport of Dangerous Goods (UN C1 test, paragraph 2.16 of the CLP (classification, labelling, packaging) Directive). To test the corrosiveness of a medium, an exposure test is performed on two materials: aluminium (non-clad 7075-T6) and carbon steel (type C1020). For each material, 3 coupons (test plates) are exposed to the medium: 

  • 1 coupon is completely immersed in the medium;
  • 1 coupon half immersed in medium;
  • 1 coupon is suspended in the vapour phase.

The test is performed at 55°C. A reflux cooling system is installed so that there is no loss of fluid during the duration of the test.

What is the ideal testing period?

The test duration can vary from 1 week to 4 weeks. Corrosion processes usually do not run linearly in time, which means that a short exposure time may give false negative or false positive results. The estimation of the required time duration should therefore be made in a well-considered way. 

How is the result evaluated according to ADR legislation?

After exposure, the coupons are cleaned and a weight loss for the three coupons of both materials is determined. The table below shows the maximum allowable weight loss as a function of the exposure time selected. These values were calculated based on a maximum allowed corrosion rate of 6.25 mm/year.


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The coupons are also thoroughly visually examined to assess and quantify localized corrosion. If localized corrosion is detected, criteria are also associated with the intrusion depth (see table below).


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The test result is positive if the maximum permissible weight loss or depth of penetration (in the case of localized corrosion) is exceeded. In this case, the corrosiveness to metals is assessed as 'Category I' and the label must be applied to the packaging, together with the hazard statement 'may be corrosive to metals'.


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If the result is negative, the corrosivity towards metals is considered "not classified" and the pictogram should not be applied in that case. Provided that the substance in the test for interaction with skin did not cause destruction across the full thickness of the skin.

Testing is not always necessary if it can be demonstrated from experience into which class the substance is classified.

Want more information on ADR legislation?

More information about ADR legislation and our tests can be found on our website. Would you like to have corrosion tests carried out so that your transport is safe? Do not hesitate to contact us and we will help you immediately!





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METALogic - Your Corrosion Partner: ADR legislation ensures the safe transport of dangerous substances
ADR legislation ensures the safe transport of dangerous substances
ADR legislation has very specific rules for the transport of corrosive and dangerous substances. Read all about the rules and testing procedures in th
METALogic - Your Corrosion Partner
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