The patented electrochemical cell built into a pen permits the non-destructive examination of individual surface areas. The small tip of the pen of approx. 1.5mm2 allows positioning the sensor on any surface geometry and thus achieving locally resolved measurements.

So far, the examination of welded pieces was restricted to special fabricated specimens or the analysis of the complete weld and the adjacent surface. The pen-type cell was used to examine welded plates made from standard stainless steel grades. The examination of the weld metal, the heat affected zone and the base materials showed the influence of the welding parameter (inert gas, heat tints, filler metal) and the post treatment applied to overcome the possible problems.

Two failures involving nickel base alloys were examined: A reaction vessel failed from attack in the heat-affected zone along the welds and a distillation column cracked along the welds. In both cases precipitations, which are only found in the transmission electron microscope, were the root cause for the premature failure of the equipment. The locally resolved electrochemical examinations are able to detect the reduced resistance in the heat-affected zones of the nickel base alloys.

Subject
Sensors, Materials, Stainless alloys, Pickling, Nickel based alloys, Sodium chloride, Heat, Pitting, Oxygen, Corrosion resistance, Stainless steel, Nickel, Heat affected zone
Keywords:
Field-testing, locally resolving electrochemical sensor, welding, stainless steel, nickel-base alloy, heat tints
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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