Hi all. New to the forum & 1st post. I've recently been put in charge of using a corrosion chamber (Ascott 450+XP) in my place of work and I've not had much experience using them. We are validating the equipment to BS EN ISO 9227:2006 (pretty much exact same as ASTM B117) using steel plates and subjecting them to a neutral salt spray test for 48 hours at 35°C. The problem I'm having is when monitoring the fallout collection the pH seems to be becoming more acidic. The pH prior to entry to the chamber was 6.9 (should be between 6.5 & 7.2 according to standard) but when I am measuring it from the external fallout collectors it is dropping to just over 5.0. I imagine it has something to do with atomisation of of the NaCl solution or the temperature change but I am not 100% certain. Would any of you good people be able to shed some light on this for me please? Many thanks in advance.