Investigation of the metal of automobile gas bottles after operation in different regions

See adjacent abstract. A comparative study was conducted on compressed natural gas automobile tanks made of 30KhMA steel after several years of use in Kazakhstan and Ukraine and on unused tanks. These 50 l tanks are made from seamless pipe of 219 mm diameter, 6.5 mm wall thickness and 1650 mm length. These tanks have been successfully used in all the republics except in southern Kazakhstan, where field failures due to cracking have occurred after a three to five year period of usage. The tanks used in the Ukraine for six to eight years did not suffer deterioration in ductility or impact resistance relative to unused tanks, but those in service for three to five years in southern Kazakhstan had significantly lower impact resistance at low temperatures. Hydrogen sulfide corrosion cracking was identified as the cause of the compressed natural gas tank failures in Kazakhstan, with the hydrogen sulfide originating from the use of impure natural gas in the Kazakhstan region.