Metal attack and dissolution of scale by mixtures o
f acids

Shalini Srivastava

Abstract

Metal attack and dissolution of scale by mixtures o f acids

Author(s): Shalini Srivastava

Calcareous deposits are formed on boiler surfaces b y continuous use of natural water. Scales formed by natural water cannot be removed easily by using single acid . Mixtures of acids were taken to observe metal att ack by acids and descaling. Experiments were conducted in such a manner that the quantity of one acid was gradually increased and the ratio of two acids was kept constant. When HNO 3 concentration was changed, lower concentration decreased rate of corrosion but higher quantities i ncreased it in HCl + H 2 CrO 4 mixture. Results obtained with different concentration of HCl showed acceleration in rate of corrosion in lower concentration of HNO 3 , H 2 CrO 4 mixture. Even in higher concentration weight loss was appreciable. In H 2 CrO 4 HCl , HNO 3 ( 90+5+5 ) respectively mixture is advantageous i.e. corrosion rate is mini mum 0.064 gm/dm 2 and scale dissolution is maximum (0.14 gm/minute).:

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