Improving the corrosion resistance of steel and alloys in coal-tar processing

Abstract

The influence of protection by means of soda on the corrosiveness of coal-tar fractions is studied. The corrosion resistance of structural materials used in coal-tar processing is determined. Besides the water present in the tar, corrosion is accelerated by hydrogen sulfide released in the decomposition of the tar’s sulfur- bearing compounds. The corrosiveness of the coal-tar fractions is determined over the height of the distillation column. The treatment of tar with sodium phenolate largely binds ammonia salts present in the coaltar emulsion and also slows hydrogen-sulfide corrosion. That reduces the corrosional losses of structural materials. Industrial tests show that the use of sodium phenolate instead of soda ensures effective corrosion protection of the equipment when its content in the tar is 0.02–0.04%. In that case, the content of sodium ions in the pitch produced will be no more than 0.005–0.0075 wt %.