volume it has also been found that it is preferred to add the inhibitor at a relatively high initial dosage rate of 2000 3000 ppm and to maintain this level for a relatively short period of time until the presence of the inhibitor induces the build up of a corrosion protective coating on the metal surfaces the corrosion inhibitor may be added either neat or diluted once the protective surface is established the dosage rate needed to maintain the protection may be reduced to a normal operational range of about 100 1500 ppm without substantial sacrifice of protection this invention will now be further described in the following examples which are provided for illustration purposes and are not intended to act as a limitation thereof a weight loss coupon immersion test was used to evaluate various compounds for naphthenic acid corrosion in the absence of active sulfur compounds a paraffinic hydrocarbon oil was deaerated with n 2 purge 100 mls min for 30 minutes at 100 u00b0 c the temperature was then raised to 260 u00b0 c and 10 3 ml of kodak naphthenic acid total acid number of the oil 5 0 mg koh g was added shortly thereafter 1 375 in 2 1018 carbon steel preweighed coupons were.