Crevice Corrosion Properties of Weld Overlays of Ni-based Alloys Compared to 6Mo Stainless Steels for Sea Water Applications*

Rogne, T.; Drugli, John M.; Solem, Tone; Salbu, Hakon; Sljellevik, Helge

doi:10.1201/9780138748104-25

Cited by 1 publication

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“…A common crevice in seawater cooling systems is a flanged joint, and it has been shown that crevice corrosion can occur here with superduplex or 6%Mo austenitic stainless steels if a suitable gasket is not selected. Francis and Byrne [52] and Rogne et al [53] have shown that PTFE creates a very tight gasket because it does not absorb water, while synthetic fibre gaskets and neoprene do, and the crevice is much less aggressive, as shown in Figure 3. Another problem can occur if the gasket contains graphite, as this is electropositive to stainless steel in chlorinated seawater and can cause galvanic corrosion on the flange face, as shown in Figure 4.…”

Section: Marinementioning

confidence: 99%

Duplex Stainless Steels—Alloys for the 21st Century

Francis¹,

Byrne

2021

Metals

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Duplex stainless steels were first manufactured early in the 20th century, but it was the introduction in the 1970s of the argon-oxygen decarburisation (AOD) steel making process and the addition of nitrogen to these steels, that made the alloys stronger, more weldable and more corrosion resistant. Today, duplex stainless steels can be categorised into four main groups, i.e., “lean”, “standard”, “super”, and “hyper” duplex types. These groups cover a range of compositions and properties, but they all have in common a microstructure consisting of roughly equal proportions of austenite and ferrite, high strength, good toughness and good corrosion resistance, especially to stress corrosion cracking (SCC) compared with similar austenitic stainless steels. Moreover, the development of a duplex stainless-steel microstructure requires lower levels of nickel in the composition than for a corresponding austenitic stainless steel with comparable pitting and crevice corrosion resistance, hence they cost less. This makes duplex stainless steels a very versatile and attractive group of alloys both commercially and technically. There are applications where duplex grades can be used as lower cost through-life options, in preference to coated carbon steels, a range of other stainless steels, and in some cases nickel alloys. This cost benefit is further emphasised if the design engineer can use the higher strength of duplex grades to construct vessels and pipework of lower wall thickness than would be the case if an austenitic grade or nickel alloy was being used. Hence, we find duplex stainless steels are widely used in many industries. In this paper their use in three industrial applications is reviewed, namely marine, heat exchangers, and the chemical and process industries. The corrosion resistance in the relevant fluids is discussed and some case histories highlight both successes and potential problems with duplex alloys in these industries. The paper shows how duplex stainless steels can provide cost-effective solutions in corrosive environments, and why they will be a standard corrosion resistant alloy (CRA) for many industries through the 21st century.

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Section: Marinementioning

confidence: 99%