54178de2_tings_and_IP_Equivalency_Chart__NEMA_Definition
[NEMA Rating] 6 [IP Equivalent] IP67 [IP Definition] 6 = Totally protected against dust [4] 7 = Protected against the effects of temporary immersion between 15cm and 1m. Duration of test 30 minutes. [NEMA Definition] 
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt; against hose-directed water and the entry of water during occasional temporary submersion at a limited depth; and that will be undamaged by the external formation of ice on the enclosure.
Rugged Technologies - NEMA Ratings and IP Equivalency Chart
NEMA Definition