Mechanism of High Temperature Corrosion by Model Naphthenic Acids
Naphthenic acid (NAP) corrosion is one of the major concerns for corrosion engineers in refineries, particularly with the increasing acidity in “opportunity crudes”. However, complex compositions of NAP in crude oil make it difficult to evaluate accurately their corrosive behavior. In the present study, several model acids, including 4-phenylbutyric acid, 1-naphthoic acid, and 4-cyclohexyl pentanoic acid, have been tested in lab scale experiments previous applied to real crude fractions. Pretreatment/challenge protocol tests the corrosive behavior of the model acids under temperature and velocity ranges close to those encountered in refineries. This work demonstrates that the pretreatment of carbon steel and 9Cralloy with model acids yields iron oxide scales with different morphology and chemical composition as determined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It is postulated that the formation of the iron oxide scale resulted from the decomposition of iron naphthenate on the surface at high temperatures.
Influencia de la estructura molecular de los ácidos naftenicos extraídos de un crudo ácido venezolano en el proceso de corrosión
Jaimes Parra,Maria Daniela(2018)Influencia de la estructura molecular de los acidos naftenicos extraidos de un crudo acido venezolano en el proceso de corrosion. Trabajo de Grado presentado ante la Universidad Central de Venezuela para optar por el Titulo de Doctor en Ciencias, Mencion Quimica
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.