Hongxia Wan

The Influence of Aluminum Tripolyphosphate on the Protective Behavior of an Acrylic Water-Based Paint Applied to Rusty Steels

The protective performance, in conditions of total immersion, of an acrylic water-based paint applied to rusty steel, has been studied using electrochemical techniques. There was no rust, blister, crack, or flake that occurred on coating after 500 h immersion. The data obtained have enabled the protective mechanism to be proposed. The specific pigments utilized in the formulation of the paint studied can release phosphates to form a protective layer on metal substrate, which can impede the access of aggressive species to substrate surface. The coatings performed electrochemical activity in the beginning of immersion; then the layer formed and resistance of coating increased.

Failure Mechanisms of the Coating/Metal Interface in Waterborne Coatings: The Effect of Bonding

Waterborne coating is the most popular type of coating, and improving its performance is a key point of research. Cathodic delamination is one of the major modes of failure for organic coatings. It refers to the weakening or loss of adhesion between the coating and substrate. Physical and chemical characteristics of coatings have been studied via scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and secondary ion mass spectrometry (SIMS). Early heterogeneous swelling at the metal-coating interface in non-defective coated metals was elucidated using frequency-dependent alternating-current scanning electrochemical microscopy. Two types of coatings (styrene-acrylic coating and terpolymer coating) were compared. The effects of thickness, surface roughness, and chemical bonding on cathodic delamination were investigated.

Effect of Zinc Phosphate on the Corrosion Behavior of Waterborne Acrylic Coating/Metal Interface

Waterborne coating has recently been paid much attention. However, it cannot be used widely due to its performance limitations. Under the specified conditions of the selected resin, selecting the function pigment is key to improving the anticorrosive properties of the coating. Zinc phosphate is an environmentally protective and efficient anticorrosion pigment. In this work, zinc phosphate was used in modifying waterborne acrylic coatings. Moreover, the disbonding resistance of the coating was studied. Results showed that adding zinc phosphate can effectively inhibit the anode process of metal corrosion and enhance the wet adhesion of the coating, and consequently prevent the horizontal diffusion of the corrosive medium into the coating/metal interface and slow down the disbonding of the coating.

Corrosion effect of Bacillus cereus on X80 pipeline steel in a Beijing soil environment

The corrosion of X80 pipeline steel in the presence of Bacillus cereus (B. cereus) was studied through electrochemical and surface analyses and live/dead staining. Scanning electron microscopy and live/dead straining results showed that a number of B. cereus adhered to the X80 steel. Electrochemical impedance spectroscopy showed that B. cereus could accelerate the corrosion of X80 steel. In addition, surface morphology observations indicated that B. cereus could accelerate pitting corrosion in X80 steel. The depth of the largest pits due to B. cereus was approximately 11.23μm. Many pits were found on the U-shaped bents and cracks formed under stress after 60days of immersion in the presence of B. cereus. These indicate that pitting corrosion can be accelerated by B. cereus. X-ray photoelectron spectroscopy results revealed that NH4+ existed on the surface of X80 steel. B. cereus is a type of nitrate-reducing bacteria and hence the corrosion mechanism of B. cereus may involve nitrate reduction on the X80 steel.

Corrosion Behavior of X80 and X70 Pipeline Steels in Beijing Soil Environment

The corrosion behavior of X80 and X70 pipeline steels in Beijing soil environment was investigated by burying test in nature field for one and two years, while using SEM and XRD analyze the micro-morphology and phase composition of corrosion products of X80 and X70 pipeline steels. The results show that general corrosion has occurred mainly on the X80 and X70 pipeline steels in Beijing soil, with the pitting corrosion. With the increase of burying time, the corrosion rate of X80 and X70 pipeline steels remain steady, and the pitting corrosion depth increases. The corrosion rate of X80 steel is lower than that of X70 steel, and the pitting corrosion degree of X70 steel is more than X80 steel. The corrosion product of X80 and X70 pipeline