Applicability of Al-Powder-Alloy Coating to Corrosion Barriers of 316SS in Liquid Lead-Bismuth Eutectic

Abstract

A new Al-alloy coating method using Al, Ti and Fe powders has been applied to 316SS in order to develop corrosion resistant coating in liquid lead-bismuth eutectic (LBE). The 316SS plates with coating layers of different Al concentrations were exposed to liquid LBE with controlled oxygen concentrations of 10 À6 to 10 À4 mass% at 823 K for 3600 ks. While surface oxidation and grain boundary corrosion accompanied by liquid LBE penetration are observed in 316SS without Al-alloy coating, the Al-alloy coating is effective to protect such severe corrosion attacks in liquid LBE. Although the coating layer containing 2.8 mass% Al does not always keep sufficient corrosion resistance, good corrosion resistance is obtained through the Al-oxide film formed in liquid LBE in the coating layer where the average Al concentration is 4.2 mass%. Cracks are formed in the coating layer containing 17.8 mass% Al during the coating process. The Al-powder-alloy coating applied to 316SS is promising as a corrosion resistant coating method in liquid LBE environment.

Development of Al-Alloy Coating for Advanced Nuclear Systems Using Lead Alloys

“…Since the formation of oxide nodes was often observed on 316SS and 410SS [17], the coating layer containing 2.8 wt. % Al does not always maintain sufficient corrosion resistance [14]. This resuit is in accordance with the report that a multilayer oxide film was formed without a protective alumina film at some places where the Al concentration in the coating layer produced by the GESA treatment was below 4 wt.…”

“…The first results of the corrosion test of the Al-alloy coated 316SS in liquid LBE at 550 °C for 1000 h have already been reported [14]. This coating method enabled us to make an Al-alloy coating layer at relatively low temperatures by the application of a eutectic reaction in a ternary Al-Ti-Fe system.…”

“…%, respectively. It was reported that dissolution of Al into LBE did not occur for the three specimens [14]. Aluminum-alloy coating Fig.…”

“…7(d). Figure 8 demonstrates the concentration profiles of Al, Ti, Cr, and Ni of Al-alloy coated 316SS using sheet material (II) after the corrosion test [14]. The concentrations of Al, Ti, Cr, Ni, and Fe were measured by point analyses using SEM/EDX.…”

“…In contrast, coating and surface treatment are promising as the method by which only high corrosion resistance is added to steels with good mechanical and irradiation properties. Several Al-alloy coating methods have been proposed for the development of corrosion resistant steels in liquid LBE [9][10][11][12][13][14]. The Al-alloy coating by a Gepulste Elektronenstrahlanlage (GESA) treatment [10,11] using a pulsed electron beam is known as a method to produce a thin and compact coating layer.…”