R. Romagnoli

Formulation and testing of a waterborne primer containing chestnut tannin

The development of a water-based pretreatment system containing chestnut tannin and phosphoric acid and the assessment of its anticorrosive properties through different conventional tests are discussed in this work. Treated steel panels coated with different paint systems were subjected to standardized (salt spray, humidity chamber, adhesion, and flexibility) and electrochemical (corrosion potential, EIS) tests. Electrochemical tests were performed by employing only panels coated with the wash primer to determine its protective effect. The binder employed in this research was prepared in the laboratory by emulsion polymerization of acrylic monomers.It was found that the tested formulation protected steel against corrosion by forming ferric tannate, which prevented oxide formation. After performing the salt spray tests, it was observed that no oxide spots developed on the scratch mark, although some blisters were detected. The good stability of the binder in low pH media (pH: 2.0–2.5) and the binder/substrate interaction are decisive factors in the performance of this aqueous pretreatment system.

Evaluation of steel/primer based on chestnut tannin/paint film systems by EIS

The influence of a tannin pretreatment applied to slightly rusted steel panels on the anticorrosive performance of alkyd paint systems has been investigated using electrochemical impedance spectroscopy (EIS) and open circuit potential measurements. From EIS and corrosion potential data analysis it was found that (1) there is not a significant influence of the tannin pretreatment on the anticorrosive protection level, which depends particularly on the barrier effect afforded by the applied paint system (however, as the corrosion process starts, tannins may cause the repassivation of steel); (2) the enhancement of the protection level afforded by the tannin primer was restricted to short immersion periods and corrosive media that were not very aggressive; and (3) water uptake was not significantly affected by the presence of the tannin primer.

Aluminum Basic Benzoate-Based Coatings: Evaluation of Anticorrosion Properties by Electrochemical Impedance Spectroscopy and Accelerated Tests

Abstract Insoluble metallic benzoates can be prepared from the corresponding soluble salts. Soluble benzoates can be used as inhibitors in neutral solutions while insoluble ones can be used as anti...

Natural products to control biofilm on painted surfaces

Purpose This paper aims to study five vegetables extracts as possible additives to control bacterial growth on indoor water-borne paints. The extracts were obtained from the weeds Raphanus sativus, Rapistrum rugosum, Sinapis arvensis, Nicotiana longiflora and Dipsacus fullonum, used in traditional medicine as antimicrobial compounds. Design/methodology/approach Weeds extracts were characterized by Fourier transform infrared spectroscopy and UV-Vis spectrophotometry. Their antibacterial activity against Escherichia coli and Staphylococcus aureus was also determined. Afterwards, selected extracts were incorporated in water-borne paints formulations. Paints antimicrobial activity was assessed against S. aureus, monitoring biofilm formation by environmental scanning electron microscopy. Findings As a general rule, results showed that tested paints were efficient in inhibiting biofilm formation, specially that formulated with Nicotiana longiflora. Practical implications The tested paints can be used to protect...