object and the gaseous mixture are short and are generally between 10 and 30 seconds preferred processing pressures are between 0 1 and 11 bars although considerably higher pressures for example 20 bars can also be used the surface roughness values that can be achieved with the process according to the invention lie between 0 4 and 0 6 u03bcm for comparison untreated or fluorinated surfaces exhibit roughness values that are several times greater the effectiveness of the process according to the present invention will be evident from the following example bottles made of hdpe hoechst ag black hostalen r 7746 with a density between 0 944 and 0 948 gg cm 3 with a volume of 500 ml were exposed on the inside and outside in an autoclave at 10 bars and at a uniform polymer surface temperature of approximately 135 u00b0 c to various mixtures of nitrogen fluorine and oxygen according to the invention contact times in all cases were 20 seconds the test results obtained are summarized in the table below ______________________________________permeation experiments with 500 cm sup 3 bottlesmade of black hostalen r gm 7746 fluorine surface finish packing densityspeci f sub 2 o sub 2 roughness g cm sup 2 men.