Search
Filters
Close

98682 IMPACT OF GRAPHITE GASKET/DUPLEX STAINLESS STEEL COUPLES ON CREVICE CHEMISTRY AND LIKELIHOOD OF CREVICE ATTACK IN SEAWATER

Product Number: 51300-98682-SG
ISBN: 98682 1998 CP
Author: A. Turnbull
$0.00
$20.00
$20.00
Electrochemical polarisation measurements have been made on a graphite laminate gasket and a superduplex stairnless steel (DSS) in deaerated 1M NaCl solution over a range of pH. The open circuit potential of the graphite ia significantly more noble than that of the duplex stairdess steel and the kinetics of the hydrogen ion reduction are greater at potentials more positive than about 0.0 V SCE. The data were used as input to a model of crevice chemistry and predictions made for potentials up to +0.4 V SCE. For crevices of parallel plates of DSS -DSS and DSS - Plastic, the usual acidic conditions were predicted but for a DSS - Graphite combination the pH was predicted to be alkaline. The latter is a consequence of the enhanced kinetics for cathodic reduction of hydrogen ions and water on the graphite which, when confiied within the crevice, act to elevate the pH. The predictions suggest that coupling to graphite, contained within the crevice, may act to preusntcrevice corrosion initiation in contrast to the usual perception of behaviour when coupling to more noble materials. In practice, there have been significant crevice corrosion failures of a super-duplex stainless steel associated with graphite gaskets. However, in all cases, the failures were in chlorinated systems for which the corrosion potentials are particularly high and beyond the range for which a benefit from graphite could be anticipated. Keywords: crevice corrosion, duplex stainless steel, graphite gaskets, seawater
Electrochemical polarisation measurements have been made on a graphite laminate gasket and a superduplex stairnless steel (DSS) in deaerated 1M NaCl solution over a range of pH. The open circuit potential of the graphite ia significantly more noble than that of the duplex stairdess steel and the kinetics of the hydrogen ion reduction are greater at potentials more positive than about 0.0 V SCE. The data were used as input to a model of crevice chemistry and predictions made for potentials up to +0.4 V SCE. For crevices of parallel plates of DSS -DSS and DSS - Plastic, the usual acidic conditions were predicted but for a DSS - Graphite combination the pH was predicted to be alkaline. The latter is a consequence of the enhanced kinetics for cathodic reduction of hydrogen ions and water on the graphite which, when confiied within the crevice, act to elevate the pH. The predictions suggest that coupling to graphite, contained within the crevice, may act to preusntcrevice corrosion initiation in contrast to the usual perception of behaviour when coupling to more noble materials. In practice, there have been significant crevice corrosion failures of a super-duplex stainless steel associated with graphite gaskets. However, in all cases, the failures were in chlorinated systems for which the corrosion potentials are particularly high and beyond the range for which a benefit from graphite could be anticipated. Keywords: crevice corrosion, duplex stainless steel, graphite gaskets, seawater
PRICE BREAKS - The more you buy, the more you save
Quantity
1+
5+
Price
$20.00
$20.00
Product tags
Also Purchased
Picture for 98702 GASKET MATERIALS AND OTHER FACTORS
Available for download

98702 GASKET MATERIALS AND OTHER FACTORS INFLUENCING THE CREVICE CORROSION RESISTANCE OF STAINLESS STEEL FLANGES

Product Number: 51300-98702-SG
ISBN: 98702 1998 CP
Author: Robert M. Kain
$20.00
Picture for 07262 Factors Affecting Gasket Selection for Stainless Steels in Seawater
Available for download

07262 Factors Affecting Gasket Selection for Stainless Steels in Seawater

Product Number: 51300-07262-SG
ISBN: 07262 2007 CP
Author: Roger Francis and Glenn Byrne
Publication Date: 2007
$20.00