A sea water hydrostatic test system for LNG storage tanks on the ground that can be completed in a short period of less than one month and whose feature is the cathodic protection of the internal wetted surfaces using Zinc-rich paints has been developed, without any risk of localized corrosion and water pollution. The galvanic corrosion and stress corrosion cracking (SCC) due to welding of different metals of 9 % Ni steel and Ni base weld metal in the internal tank vessel can be prevented by applying inorganic zinc or zinc primer and zinc tape. Their corrosion prevention performance has been confirmed by the sea water immersion test and the salt spray test. By the SCC test and the slow strain rate test (SSRT), the water quality criteria such as H2S concentration, pH value that SCC is not generated in the sea water have been also verified. It has been shown that the corrosion prevention method using zinc-rich paints does not cause any effluent pollution of zinc and this method is an improvement over the conventional cathodic protection method using sacrificial zinc anodes or impressed current cathodic protection.

Subject
Corrosion prevention, Immersion tests, Water, Materials, Cathodic protection, Iron, Water immersion, Steel, Water pollution, Hydrostatic testing, Zinc, Stress corrosion cracking, Paints
Keywords:
LNG storage tank, cathodic protection, sea water, galvanic corrosion, stress corrosion cracking, 9 % Ni steel, zinc-rich paints, MIC, HIC, hydrostatic test
© 2006 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2006
Association for Materials Protection and Performance (AMPP)
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