China
Africa
Explore chapters and articles related to this topic
Types of Corrosion in the Offshore Environment
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
6MO (UNS S31254) is a super austenitic stainless steel with a relatively high level of molybdenum (6%) and nitrogen, which provides a high level of pitting and crevice corrosion resistance. The resistance of a material to pitting and crevice corrosion is measured by pitting resistance equivalent number (PREN). There are several formulas for PREN calculation, but the simplest one correlates the PREN to three elements in the material: chromium, molybdenum and nitrogen. Equation 1.4 expresses this basic PREN calculation.
Corrosion
Published in Mavis Sika Okyere, Mitigation of Gas Pipeline Integrity Problems, 2020
Stainless steel: Steel alloyed with at least 10% chromium is called stainless steel. The addition of chromium causes the formation of a stable, very thin (few nanometers) oxide layer (passivation layer) on the surface. Stainless steel therefore does not readily corrode or stain when in contacts with water like carbon steel does. But, under some circumstances, the passivation layer can break down, causing local attacks such as pitting corrosion. Pitting corrosion, the predominant form of corrosion of stainless steel, does not allow lifetime prediction as is possible with zinc coatings. The resistance of stainless steel against pitting corrosion can be roughly estimated by the PREN (pitting resistance equivalent number). The PREN is based on the chemical composition of steel, taking into account the amount of chromium, molybdenum, and nitrogen. In literature, various equations for this calculation are given. The most common equations are: For stainless steels with Mo < 3%PREN=%Cr+3.3×%MoFor stainless steels with Mo ≥ 3%PREN=%Cr+3.3×%Mo+30×%N
Effect of nitrogen on microstructure and corrosion resistance of Cr15 super martensitic stainless steel
Published in Corrosion Engineering, Science and Technology, 2019
Ruijin Chang, Jingyuan Li, Jinbo Gu
At the same time, nitrogen, as a cheap strengthening element, can improve the strength of martensite stainless steel by means of solid solution strengthening, precipitation strengthening and fine crystal strengthening [13–15]. What’s more, nitrogen also has a certain influence on corrosion resistance [15–17]. In the pitting resistance equivalent number [18] (PREN = %Cr + 3.3%Mo + 30%N), nitrogen plays a positive role in improving pitting potential of stainless steel. Some researches show that nitrogen can improve the stability of passive film of stainless steel [19]. Meanwhile, it can reduce the activity of Cr and inhibit the precipitation of carbides in the grain boundaries, thus reducing the depletion of Cr [20,21]. However, these effects are limited to nitrogen precipitated in the form of small precipitates or in a solid solution state. Nitrogen is still an important austenite-forming element, and its ability to expand and stabilize austenite phase area is about 25 times that of Ni element [22], playing a decisive role in martensite phase transformation. Studies [23,24] have shown that nitrogen significantly increased the austenite content in the process of heat treatment in SMSS. However, little research has been done to SMSS in the change of its corrosion resistance which results from phase transformation caused by the addition of nitrogen. Therefore, in the paper, a certain amount of nitrogen was added to study the effect of nitrogen on the microstructure and corrosion resistance of the Cr15 super martensite stainless steel.
Corrosion-resistant alloy testing and selection for oil and gas production
Published in Corrosion Engineering, Science and Technology, 2018
Narasi Sridhar, Ramgopal Thodla, Feng Gui, Liu Cao, Andre Anderko
ISO 15156 provides a number of guidelines for the selection of CRAs for sour service [11]. The localised corrosion resistance of the CRAs is often ranked by the pitting resistance equivalent number (PREN), which is given by (wt-% Cr+ 3.3 wt-% (Mo + 0.5 W) + 16 wt-% N) [11]. The correlation of PREN to localised corrosion susceptibility is dependent on the chloride concentration and the corrosion potential, but is used as way to rank the alloys. The limits of SCC resistance are given in terms of chloride concentration, temperature, pH, and H2S partial pressure [11]. The resistance of CRAs for SSC and HSC are given more qualitatively in ISO 15156. These limits were established through a combination of laboratory studies and field experience.
A study on the intergranular corrosion and pitting resistance of Inconel 625 coating by PTA-P
Published in Corrosion Engineering, Science and Technology, 2019
Raphael Amorim Lorenzoni, Ricardo Paris Gasparini, Ana Cláudia dos Santos, Temístocles de Sousa Luz, Marcelo Camargo Severo de Macêdo
Aiming to evaluate the pitting corrosion susceptibility, the pitting resistance equivalency number (PREN) is conventionally used in literature as an empiric index that correlates the alloy pitting corrosion resistance with its chemical composition through Equation (4), where higher PREN values represent higher pitting corrosion resistance in chlorides.