Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985 and performed well after 15 years. Anodes were inexpensive and repairs easy. Depolarization potentials are consistently above 100 with long-term current densities around 2 mA/m 2. Bond strength remains adequate.
A case history is described involving microbiologically influenced corrosion (MIC) of AISI Type 304L stainless steel piping failure after being in contact with untreated stagnant, low chloride potable water for nine months. Specialized microbiological analysis techniques, including scanning electron and optical cmicroscopy, were used in the failure analysis.
Laboratory exposure testing of carbon steel to water from different regions of the United States, with varying chemistries and chloride content. The results of chemical analyses conducted in the laboratory, including elemental analysis by SEM/EDS and analysis by x-ray diffraction are correlated to water chemistry.
AZ31 (UNS M11311) is a wrought magnesium alloy used in aerospace and automotive applications. In this work, KOH-based electrolytes were used to study the corrosion behavior of AZ31 alloy in highly alkaline environment. The effect of dopants and exposure time on pit initiation was studied via optical and scanning electron microscopy.
This work details the failure analysis of a super duplex valve (UNS J93404)(1) ASME(2) class 1500, operating in treated sea waters with high chloride content below 80°C. A detailed analysis of the microstructure, fracture surfaces and mechanical properties was combined with studies of corrosion resistance of different regions by means of immersion tests (ASTM G48)(3)33, electrochemical analysis and polarization tests (large scale and with a micro-cell). Selection of base material was performed according to Table A.24 of NACE MR0175/ISO 15156-3(4).
The cast material presents a segregated microstructure containing ferritic phases with different pitting resistance equivalent number (PREN); this strongly affects the corrosion properties of the material, enhancing the susceptibility to localized corrosion and leading to a Stress Corrosion Cracking (SCC) mechanism.