A Study of Corrosion of Steel Under a Variety of Thermal Insulation Materials

Abstract

Corrosion of steel equipment under thermal insulation is and has been a costly problem in Union Carbide Corporation (UCC) chemical operations as well as other refining and chemical plants throughout the world. The Materials Technology Institute (MTI) has spent about $30 thousand trying to develop a nondestructive inspection method to detect and measure corrosion under insulation. The corrosion rate of carbon steel under insulation depends upon a number of variables: moisture, oxygen availability, metal temperature, paint system, and the insulation. Little work has been published that defines the effects different types of insulation have on the corrosion rate of carbon steel. Some suggest that the type of insulation does make a difference. An in plant test was designed and operated to obtain quantitative data comparing several types of insulation and their effect on corrosion of steel. Twelve pieces of insulation were applied to carbon steel pipe and were exposed to the atmosphere at Texas City, TX. Water, in addition to rain, was occasionally added to the outside of the pipe, and steam was run through the inside of the pipe once a week in order to accelerate the corrosion rate. This paper will report qualitatively and quantitatively on the corrosion rates of the carbon steel under the various types of insulation. The data will be useful to insulation specialists in guiding their selection of the kind of insulation from the standpoint of its influence on steel corrosion.