The corrosive-to-metal property of substances and mixtures as evaluated by use of the UN C1 test
Résumé
One key development in the ECORBIO project was to evaluate the interest for our study of the UN C1 test protocol, which recently gained enlarged official application in the context of the so called Global Harmonized System (GHS) also known as the purple book [1] and related transposition regulations all over the world. As an example, GHS has been transposed in the CLP Regulation in the EU [2]. Originally, the UN C1 test was referred to in the Recommendations on the Transport of Dangerous Goods [3] also developed by the same Committee of the United Nations in Geneva, in 2002. The test supports a conventional evaluation of corrosive environment induced by a given chemical on two types of metals (one carbon steel and one aluminum), considers two types of corrosion phenomena (regular and pitting) ending by a pass/fail criteria to decide from a regulatory viewpoint whether or not a given substance or product shall be considered as corrosive to metal and be labeled and packed for transport accordingly in Class 8 of corrosive substances. In a first part, the presentation aims at reminding the history of development and the dual context of implementation of this test as well as providing a description of the test protocol and of the current criteria for its official application. In a second part, an evaluation of its pertinence for providing useful information about corrosive potential of key chemicals and industrial juices inside biorefinery metallic equipment is also presented, entailing calibration issues, examining operational issues in terms of test equipment and test protocol, actual testing on vinasses and carboxylic acids (see also lecture 4), and comparisons with results from other screening tests developed in other contributions relating to the ECORBIO project. Whereas some limitations of the UN C1 test was already outlined by present authors in their former contribution to the CLP guidance published by the European Chemical Agency [4], our analysis confirms some of these limitations in practice in terms of i) feasibility of maintaining an operating temperature of 55°C within a limit of ±1°C variation ii) obtaining useful information about genuine corrosion hazards in the context of biorefining with this test, especially if the current “pass/fail” criteria are maintained at its original value (6.25 mm mass loss /year) defined in the context of TDG transport. In conclusion, perspectives towards a more reliable and efficient use of the UN C1 test is discussed.