Recent Patents on Corrosion Science - Volume 3, Issue 1, 2013

A simultaneous in situ optical microscopy and simultaneous electrochemical analysis method is presented for studying 316L stainless steel in hydrometallurgical process solutions. The electrochemical method involved potentiodynamic analysis of the 316L stainless steel surface in aerated and deaerated experimental hydrometallurgy process fluids. This technique is reviewed along with other potentiodynamic methods used in stainless steels, recent patents on stainless steel technologies, and the results are discussed in conjunction with various theories and applications. The results illustrate a wide variety of corrosion behaviors (active, passive, anodic knee) and parameters (corrosion rate, pitting potential, mixed potential, pH) possible for 316L stainless steel under potentiodynamic test conditions. Analysis of these samples provides both a detailed visual account of the corrosion process in addition to standard electrochemical analysis regarding pitting potential, corrosion potential and corrosion rate. Polarization data and analysis with respect to the corrosion patterns observed is presented including in situ images of surface layer changes, etching, pitting and microstructure. Analysis of copper sulfide inclusions and metal surface film behaviors in solution were performed showing the tendency of inclusions and film to dissolve and act as nucleation sites for pits. The proprietary experimental hydrometallurgical process fluids tested further support the ability of in situ optical microscopy to successfully image and provide valuable insights into the corrosion processes taking place.

The development of hybrid materials is desirable given that combinations of polymers and inorganic materials can be self-assembled forming pre-ordered complex structures with precise mechanical, chemical and electrical programmable properties. These new materials possess new and/or enhanced properties. For instance, polymeric materials are widely used in industry because of their superior properties such as flexibility, resistance to biochemical attack, good biocompatibility, lightweight, and inertness. In this work, synthesis, characterization and electrochemical noise evaluation of hybrid materials casted from nylon 6-6 and titanium are carried out for a patent application. Synthesis was carried out with different % weight of titanium functionalized with APTES. The materials obtained here were characterized through scanning electron microscopy (SEM), thermal analysis (TA), infrared spectroscopy (IR) and electrochemical noise technique in Hank solution to simulate the internal fluids of the human body, looking forward to biomaterial applications. SEM shows a homogenous material. Concentration of titanium was verified with TA. IR spectra show differences between Ny-Ti at different concentrations. Results also showed that hybrid materials made with 50%wt titanium present the lower resistance and the 40% wt the highest, as was confirmed by electrochemical noise resistance.

Elaborations in the field of chemical and abrasion resistant coatings and composite polymer materials by company Polymate LTD.-INRC (Israel) and its employees are reviewed. The main fields of advanced corrosion resistance materials are liquid and water based rubber compositions, hybrid nonisocyanate polyurethane coatings, nanostructured organic-mineral coatings. The review includes patents used by the industry of several countries of Europe, USA, Canada and Asia.Chemical resistant materials, abrasion resistant materials, polymeric materials for coatings, hybrid nonisocyanate urethane-epoxides, nanostructured hybrid oligomer composition, rubber-based compositions, organic-mineral coatings.

The discovery of the first petroleum off-shore fields 30 meters below sea level in the Brazilian coast in 1968 stimulated the development of new technology for oil extraction and production in increasing water deepness. Outstanding levels such as 6000 meters were expected for oil extraction in the offshore pre-salt reservoirs in the 2010s, which demanded a large amount of material, raising costs to extremely high levels. So, considerable new research efforts are being directed towards the development of new martensitic steels, with improved properties as a lower cost option for such application. In the present work information is gathered about recent developments on new martensitic stainless steels capable of withstanding severe conditions of operation and exploration of petroleum in marine platforms. These materials must present adequate mechanical strength and corrosion resistance in these conditions. With this purpose such information, based on articles and patents published in international databases since the onset of the 21st century (2001) until 2012, is compiled and analyzed in this review article.

This article deals with the effective attributes of friction material application out of aluminum matrix composites (AMC) containing disperse ceramic phase, particularly SiC particles, via literature survey and result analyzing of the relevant research works. These properties include thermal expansion coefficient, wear, friction coefficient, mechanical and thermal strength, durability, etc. The wear mechanism of braking in brake pads is discussed to perceive the material behavior of the friction pad constituents and phases to ameliorate the vehicle's brake pad performance considering its main tasks. The discussion elaborates the advantages and the disadvantages of AMC as friction material based on the essential brake pad properties defined by automotive standards parameters and the vehicle industries requirements. Analysis of the results presented in this paper suggests that the optimized reinforced AMC may result in a new patent for friction material applied in the vehicle brake pad.

The poor corrosion resistance of magnesium alloys is limiting their widespread applications. Some patents and literatures have reported corrosion-resistant magnesium alloys and surface treatment techniques to improve the corrosion resistance. However, these acknowledges are not enough for well understanding the corrosion behavior of magnesium alloys in actual application environments. In this paper, the influence of Cl- on the corrosion rate of AM50 alloy in simulated acid rain (SAR) was studied using electrochemical tests and scanning electronic microscopy (SEM) observation, and then the corrosion mechanism of magnesium alloys in the acid solution was established. The results show that Cl- can accelerate the corrosion of Mg matrix around the AlMn phases in the initial stage of corrosion. The predominant corrosion type of the AM50 alloy is the uniform type of corrosion in SAR. The coverage fraction of Mg(OH)2, MgH2, and the concentration of Mg+ are three key factors influencing the corrosion processes of magnesium alloys in SAR.

The phenomenon of corrosion of metals including Fe, Al, Cu, Zn, Mg and their alloys is controlled to a great extent by selection of highly corrosion resistant inhibitors. The associated cost factor favors the use of cheap metallic materials along with efficient corrosion prevention methods in many industrial applications. In this aspect, corrosion inhibitors have a significant role in the protection of metals from corrosion. These inhibitors are either hazardous chemicals or environmentally friendly chemicals. Many authors reported that the use of plants extracts from mango, cashew, passion-fruit, orange, khillah seeds, African bush pepper, neem leaves and papaya as corrosion inhibitors in an acid medium for protection of metals such as steel, copper, and copper alloys gave high inhibition efficiency. Some environmentally friendly chemicals namely, octanoic acid, 2-ethylhexanoic acid and their alkali salts, sodium borates, triazoles, hydrocarbyl, and benzotriazoles were used as corrosion inhibitors. Polymeric compounds such as polyacrylic, polymaleic, and polyaspartic acid and its salts were also used as corrosion inhibitors for acidic ferrous metal surfaces in contact with acidic corrosive aqueous saline environment saturated with carbon dioxide. Published patents related to the corrosion inhibition using green corrosion inhibitors are discussed.