Vincent F. Hock

Development of a Predictive Corrosion Model Using Locality-Specific Corrosion Indices

Abstract : This Office of the Secretary of Defense Corrosion Prevention and Control Program project developed a statistical model of atmospheric corrosion of selected metals. This model relates measured corrosion rates at test sites (mainly military bases) worldwide to critical environmental variables. These variables are (1) a measure of atmospheric chlorides, (2) rainfall, and (3) relative humidity values at several levels. The measured corrosion rates obtained at test sites over the period of CY05 - CY07. Additionally this database includes much more data obtained from similar DoD monitoring activities over nearly the last decade. This serves to enhance the statistical relevance of the developed model. The model includes algorithms for several metals that have been routinely used in the monitoring work. These include copper, 6061 T6 aluminum, 7075 T6 aluminum, and a low carbon (1010) steel.

Electro-Osmotic Pulse Technology for Corrosion Prevention and Control of Water Intrusion in Below Grade Concrete Structures

In below-grade buildings and buried structures, such as those constructed as hardened secure facilities and used for munitions storage on U.S. Army installations, water intrusion can cause serious damage and reduce penetration resistance. Inside the building active water and high humidity can result in corrosion of HVAC, electronic equipment, as well as damage or disrupt mission critical electronic equipment. In the adjacent backfill and the structure itself, excessive water can seriously compromise the structural hardening of the facility. Thus, it is vital to Army sustainability to control moisture in below-grade structures and eliminate corrosion of electrical mechanical equipment. This also prevents mold growth on the interior surface of below grade concrete walls and floors. Control of water movement involves both actively removing water in and around a building, and the use of barriers to prevent water from penetrating to interior spaces. A pumping system is typically required with the use of a barrier system to assist in controlling the movement of moisture into the structure. Conventional waterproofing technologies are expensive and often have short service life. A new approach is needed—a cost effective and robust solution—to the pervasive problem of water intrusion. Electro-Osmotic Pulse is a promising alternative solution presented here. Electro-Osmotic Pulse (EOP) technology uses pulses of electricity to reverse the flow of water seepage. The applied voltage causes moisture to flow out of the basement walls and away from the building. The technology works by alternately pulsating a direct electric field with an off period. The first part of the sequence consists of a pulse of positive voltage (as seen from the dry side of the concrete wall), followed by a pulse of negative voltage. This is followed by a period when no voltage is applied. Of the three parts, the positive voltage pulse has the greatest time duration. The amplitude of the positive signal is typically on the order of 20 to 40 Volts DC. This electrical pulse causes cations (e.g., Ca++) and associated water molecules to move from the dry side (anode) towards the wet side (cathode) against the direction of flow induced by the hydraulic gradient, thus preventing water penetration through buried concrete structures. Laboratory and field tests have shown an increase in calcium compounds at the cathode side of test specimens. The negative portion of the pulse increases the efficiency of moisture movement by depolarizing the electrodes. Electro-Osmotic Pulse (EOP) technology has been successfully installed in military structures such as family housing, steel reinforced deep structures, and tunnels. EOP has also been implemented on Civilian structures such as residential structures, D.C. Metro Tunnels, and an underground treasury vault. EOP has been shown to prevent moisture seepage into below-grade structures. It is effective at keeping concrete surfaces at or below 50 percent humidity content, meaning the treated space stays dry, indoor relative humidity stays low, and no mold or mildew can grow. This technology has received the 2002 international NOVA award for innovation in construction, and twice nominated for the CERF Pankow award (1999 and 2004). The ERDC research on this technology has also been recognized by the 2004 Army Research and Development Achievement Award.

Use of Small-Scale Electro-osmotic Systems in Controlling Groundwater Movement Around Structures

Small-scale electro-osmotic systems for use around commercial and residential structures are becoming increasingly common as a method of controlling the water seeping through concrete foundations or seeping into basements and other underground structures. These systems are designed for continuous use in moving water out of the soil adjacent to the structures. There is little engineering guidance on the selection and installation of the components for these small-scale systems. Features such as soil conditions, positioning of electrodes, operating voltages, operating patterns for decreasing polarization problems, and selecting the types of electrodes are critical in assuring efficient operation and a long service life. By screening sites to make sure that the geological conditions are appropriate and tailoring the system to fit the site, electro-osmotic dewatering can be applied safely and effectively, giving a property owner a method other than conventional drains for controlling groundwater problems on a building site.

Infilling of Pore Spaces in Mortar Using Electrically‐Driven Solution Transport Systems

It has been widely established that all types of conventional concrete can be strengthened by reducing the porosity of the concrete matrix. Attempts to infill the pores by converting reactive phases such as calcium hydroxide into calcium carbonate have been partly successful, but the success of this approach has been limited by the amount of Ca(OH)2 produced in the hydration of the concrete and by the positions of the new crystalline phases that are formed. These limitations can be overcome by using a combination of electrophoresis to move particles into concrete pores and the use of ion transport to move new dissolved reactants into the concrete mass. Bench scale experiments have demonstrated that significant density and strength increases can be obtained by electrophoretically moving seed crystals of selected mineral phases such as calcite, aragonite, or vaterite into the larger pores in concrete and then using a low‐voltage DC current to migrate in calcium and carbonate ions to grow the selected crysta...

Green Chemical Treatments for Heating and Cooling Systems

Scale, corrosion and the and biological growth in industrial water handling processes result in reduced water flow though pipes, reduced heat transfer, and pump failures. Preventative treatments for these problems are based upon chemical compounds that are most often toxic and environmentally persistent. Manufacturers continue to introduce new chemicals and treatment programs onto the market, and old products have been discontinued. Many manufacturers claim that the new chemical and treatments are more environmentally friendly and safer for the plant workers and the users. The U.S. Army Engineer Research and Development Center Construction Engineering Research Laboratory has undertaken a research effort to look at these new chemical treatments. The objective of this work was to develop “green” water treatment chemicals that control biological growth, corrosion and scale while reducing or eliminating the generation of toxic substances during the manufacture, use, and disposal processes.

Combined Structure Geometry and Anode Placement Effects on Cathodic Protection Effectiveness

An impressed current cathodic protection system was applied to an uncoated test sample. The test sample was chosen to represent an essential right angle feature of a common structure. Anode placement was quantitatively shown to affect the resulting surface polarization distribution. Two distinct types of local polarization depletion zones have been demonstrated. These regions of lesser polarization represent a locally insufficient amount of cathodic protection compared to criteria designated values. Conversely, for geometrically complex structures containing sharp features, the possibility of locally evolving hydrogen gas is also discussed.

Corrosion Control Cost Reduction through Improved QA Information Management - An OSD Funded Joint Navy Army Initiative

When the coating application does not meet the required standards, the lifetime of the coating can be substantially reduced. In the worst case, the coating may catastrophically fail immediately after being placed into service. This ongoing joint project conducted by the U.S. Navy and the U.S. Army is intended to demonstrate and provide for the automation of data collection for painting projects on critical structures and the make this data a more effective resource for making effective management decisions for the protection of DoD assets.

Rapid Soil Stabilization and Strengthening Using Electrokinetic Techniques

Abstract : The Army has a requirement to develop methods of strengthening soil to support rapid runway and roadway construction. A study was undertaken on the use of DC current applied to soil to form cementing phases in the soil. Preliminary work was on the use of zinc. aluminum. and iron in a variety of granular materials. Metal ions primarily form soft metal hydroxide gels that produce no immediate soil strengthening. Passing current through soil mixed with an alkali-reactive silicate produces rapid hardening with strength to 2,000 psi.