Proposed new AFNOR specification

Association Française de Normalization (AFNOR) manages the Norme Française (NF) specification for on-road engine coolants NF R 15-601 which has last seen an update in 1991. Since then coolant and vehicle technologies have evolved vastly, and Arteco has contributed to the much-needed modernization of this document through the French institute Groupement Française de Coordination (GFC).

In contrast to its current form, the proposed AFNOR specification does not limit products to MEG based technologies. The AFNOR specification defines three types of engine coolants according to the table below. The density and refractive index of coolants in the current specification have hard limits, which in conjunction with freeze point limits restrict the three types to MEG based technologies. The new version requires density and refractive index to be reported but sets no limits, meaning that coolants with base fluids apart from MEG, such as MPG and glycol free products, can fall under coolant types 2 and 3.

Because of powerful shifts in inhibitor technologies in past decades, many of the specifications of the AFNOR have had to be dramatically altered.

Reserve alkalinity (RA) has long been used with traditional inhibitor technologies to provide an indication of total inhibitor quantity and the resistance of a coolant to acidification, but with new inhibitor technologies based on organic acids using RA to assess product quality can be misleading.

In the proposed new AFNOR specification, the RA and full titration curve must be reported, but no hard limit is set, providing flexibility for new technologies whilst reassuring customers accustomed to this method. Similarly the pH range accepted for coolants has been expanded at the higher end from 8.5 to 9 to include new technologies that provide good protection at higher pH. A polarization resistance test present in the old specification is removed for similar reasons. This test assesses protection provided by layer-forming inorganic inhibitors and has no relevance to long-life coolant technologies now more prevalent on the market.

Corrosion testing is modernized by increasing corrosive severity and taking into account shifts in alloys present in the cooling system. For glassware corrosion testing the temperature has been adapted. In the coupon set, solder is removed in favour of an additional aluminium alloy and limits on aluminium have been made more stringent to reflect the move toward lighter metals. The hot surface corrosion test is now run with a water of increased corrosivity but stays otherwise the same. A new test method for high temperature stability of a coolant is introduced. This test assesses both oxidation stability and the tendency for high temperature aluminium corrosion.

Specifications for foaming tendencies were not part of the 1991 document and are now introduced. A foam test at room temperature similar to CEC C 10-X-97 is added as well as a foam test at 88°C similar to ASTM D1881. The first test mimics foaming during first-fill as the coolant is injected into the cooling system. The second test is more relevant for the aftermarket.  As the new document details the two tests, the specification has been written so the coolant manufacturer can choose which test is more relevant for their product and its usage.

The AFNOR NF R 15-601 specification for on-road engine coolants was in great need of modernization, and the broad strokes of this effort are presented here. The updated specification is more relevant to coolant technologies present at this time and hones in on new important factors for a coolant in the 21st century.