Inhibition of corrosion driven delamination on iron by smart-release bentonite cation-exchange pigments studied using a scanning Kelvin probe technique

Low-cost, environmentally friendly, cation exchange pigments derived from naturally occurring bentonite clay are shown to significantly enhance resistance to corrosion-driven cathodic delamination in organic coatings adherent to iron surfaces. A scanning Kelvin probe (SKP) is used to study the delamination kinetics of pigmented and unpigmented poly-vinyl-butyral (PVB)-based coatings applied to polished iron substrates. The bentonite clay is used both in its native form and exhaustively exchanged with a range of divalent alkali earth and trivalent rare earth metal cations. For the best performing divalent cation-exchanged pigment, the dependence of coating delamination rate on pigment volume fraction is determined and compared with that of a conventional strontium chromate (SrCrO4) inhibitor. An inhibition mechanism is proposed for the bentonite pigments whereby underfilm cation release and subsequent precipitation of sparingly soluble hydroxides reduces the conductivity of the underfilm electrolyte

Inhibitive effect of sodium (E)-4-(4-nitrobenzylidenamino) benzoate on the corrosion of some metals in sodium chloride solution

The inhibition performance of a novel anionic carboxylic Schiff base, sodium (E)-4-(4-nitrobenzylideneamino)benzoate (SNBB), was investigated for various metals, namely low carbon steel F111, pure iron and copper, in neutral 10 mM NaCl solution. Potentiodynamic polarization, scanning vibrating electrode technique (SVET), quantum chemical (QC) calculation, and molecular dynamics (MD) simulation were employed. The potentiodynamic polarization data showed that SNBB acts as an effective corrosion inhibitor for both iron and F111 steel, but it is not effective for the copper. In situ spatially-resolved SVET maps evidenced a major change in surface reactivity for Fe and F111 steel immersed in 10 mM aqueous solution in the absence and in the presence of SNBB. Featureless ionic current density distributions were recorded in the presence of SNBB at both their spontaneous open circuit potential (OCP) and under mild anodic polarization conditions, while major ionic flows were monitored above the metals in the absence of SNBB. On the basis of computer simulations, it is proposed that SNBB produces a stable chelate film on iron and steel surfaces that accounts for the good corrosion inhibition efficiency observed. The different inhibition efficiencies of SNBB molecules on the iron and copper was attributed to the special chemical structure of SNBB molecule and its different chelation ability with the released metal ions on the metal surface. The QC calculations also confirmed the high corrosion inhibition efficiency of SNBB. The MD simulation indicated higher binding energy of SNBB on iron surface compared to that of copper surface. The interaction mode of SNBB on iron and F111 steel surfaces corresponds to a mixed chemical and physical adsorption, and it obeys the Langmuir isother

Characterization of the corrosion resistance of duplex stainless steels using local current density mapping techniques

An in situ investigation of the dissolution behavior of duplex stainless steel has been carried out in acidic solutions containing 2.0 M HCl with 2.0 M H{sub 2}SO{sub 4} to determine differences in dissolution rates of the austenitic and ferritic phases. The current density distribution over the dissolving steel surface was measured using a vibrating electrode. The study demonstrated that this technique could quantify the differences in dissolution rates of the austenitic and ferritic phases under the conditions tested. The dissolution rates for the two phases peak at different potentials resulting in multiple current maxima. In addition, transients in dissolution behavior of the two phases at different potentials were observed using optical microscopy. Electron microscopy of the dissolved surface showed very high levels of aluminum and silicon enrichment on the austenitic phase

Repassivation Studies of Aluminum Using a Rotating Strip Electrode

In this work a technique was described to study the repassivation of bare metal surfaces. The advantage of this approach over other techniques is the ease with which multiple repassivation events can be studied. The repassivation rate of aluminum was found to depend on the anion in solution. Repassivation rates are higher for aluminum in phosphate and sulfate solutions compared to borate. It is possible that borate may interact more strongly than sulfate or phosphate on the bare aluminum surface blocking the diffusion of oxygen or changing the rate of repassivation

The environmental impact of the zero energy ready home program on manufactured housing

Manufactured homes, which are built in the factory and shipped to the site, provide economical housing for more than 20 million Americans. To improve energy measures and facilitate deployment of renewable energy systems to achieve net zero energy in manufactured homes, the U.S. Department of Energy (DOE) made public the Zero Energy Ready Home (ZERH) National Program Requirements for manufactured housing in 2022. To understand how these changes will impact the environment and the building’s durability, life cycle assessment and hygrothermal simulations were carried out for a standard manufactured home design and two ZERH designs in Knoxville, Tennessee. The embodied carbon and operational emissions were compared for the standard design and two ZERH designs for a service life of 60 years. Operational emissions were determined using the Building Energy Optimization tool, BEopt, and durability assessment was carried out using WUFI Pro. Life cycle assessment was performed in accordance with ISO 14040 using Athena’s Impact Estimator for buildings. Results indicate that the investment in embodied carbon of the zero energy ready homes is small relative to the savings in operational emissions. The increase in embodied carbon in the zero energy ready homes is offset by the reduction in operational emissions compared to the standard home for the first year of operation. With an investment of 59 kg CO2 eq in embodied carbon, the reduction in operational emissions is approximately 680 kg CO2 eq after one year compared to a construction that meets the prescriptive performance of the building code for manufactured housing