Estimation of protective ability, physical and mechanical properties of polymer inhibited films

Metal products are subjected to atmosphere corrosion during transporting and longtime storing. Utilization of packing materials eliminating the access of water vapor and aggressive gases to the metal products surface is an important ways of struggling against the corrosion. Among the methods of metal products protection against the corrosion, application of volatile inhibitors is one of most effective one. As a carrier of the volatile corrosion inhibitors, polyethylene films can be used. Study of strength and barrier properties of polyethylene films with a volatile corrosion inhibitor and without it accomplished. As an object of the study, the films, produced under laboratory conditions by extrusion with blowing of low-density polyethylene and mixture of low-density polyethylene and IFKhAN volatile inhibitor, developed by the Institute of Physical Chemistry (Academy of Sciences of RF). For accelerated corrosion tests, samples of 08пс cold rolled steel used. The prepared samples packed in the studied films, a part of the closed airtight, and another part – not compact. It was traced, that the samples packed in the polyethylene film without the volatile inhibitor, had a point corrosion. The airtight sealed polymer film casings protect the carbon steel much better, comparing with the not compact casings. The surface of samples corrosion worms, which were airtight packed, was 0.15%, not compact ones – 0.33%. When inhibited polymer film was used for not compact packing, the corrosion had a uniform character, no local corrosion worms (pitting) was observed. The corrosion products were spongy, weekly cohered with the basic metal, easily peeling off. During the test period, the samples airtight packed in polyethylene film, containing IFKhAN volatile inhibitors, had no areas of corrosion. It was found, that input of inhibitor into the polyethylene matrix results in decreasing the film strength properties due to formation structure defects at the sub-molecular level during the extrusion, and also as a result of inhibitor desorption.

Modeling of corrosive atmospheres for evaluation of the efficiency of volatile inhibitors

A method of modeling aggressive atmospheres used for different tests in corrosive environments close as possible to actual full-scale conditions is proposed. The method provides simulation of air atmospheres containing gaseous corrosion stimulants (CS) as microcomponents of air. The content of SCs in such atmospheres (both separately and together) can be set and maintained at an unchanged level within a wide range for as long as desired. The method is based on Henry’s equation characterizing concentration of the gas dissolved in a liquid phase as a function of the gas partial pressure in the equilibrium gas medium with allowance for the solubility of the corrosion stimulants in water in conditions under consideration. The procedure is easy to use and does not require long special training. Samples of corrosion stimulants NH3, CO2, and H2S are considered. Experimental results characterizing the corrosion rate of St3 carbon steel and copper with one or several CS simultaneously present in air atmosphere, as well as data on the efficiency of volatile inhibitors of «IFHAN» series under similar conditions are presented.