A benzoxazine/substituted borazine composite coating: A new resin for improving the corrosion resistance of the pristine benzoxazine coating applied on aluminum

In this paper, laboratory synthesized Phenol-paraPhenyleneDiAmine (P-pPDA) benzoxazine containing different amounts of B-trimesityl-N-triphenylborazine was applied by spin coating on aluminum and thermally cured. The addition of the borazine derivative (borazine 1) does not appear to modify the curing characteristics of the P-pPDA matrix itself as shown by FTIR, DSC and DEA analyses; however, some interactions - chemical and/or physical (co-crystallization) – between P-pPDA and borazine 1 cannot be excluded. The microstructure of the composites is characterized by a two phase system consisting of a dispersion of nanosized (10–20 nm) clusters for the lowest borazine 1 concentration (0.5 wt%), evolving towards bigger (100–200 nm), agglomerated clusters for higher borazine 1 concentrations (3 wt%) and finally, continuous, dendritic structures within the P-pPDA matrix for the highest borazine 1 concentration (10 wt%). The benzoxazine composite coating containing 0.5 wt% trimesitylborazine derivative showed a largely increased and durable ability to protect the aluminum substrate. It is shown that a highly capacitive behavior and durable barrier properties can be obtained for P-pPDA coatings containing such a low amount of borazine derivative homogeneously dispersed in the benzoxazine matrix. For concentrations of 3 wt%, as agglomeration took place and dendrites appeared for the highest concentration of borazine derivative (10 wt%), the corrosion resistance decreased with time

Novel promising way to synthesize non-isocyanate polyurethanes (NIPUs) for innovative coating applications against corrosion protection of metal surfaces

Polyurethanes (PUs) are one of the most widely used polymeric materials with applications in automotive, as sealants, adhesives, decorative, aircraft topcoats, for coatings or as foams for thermal and/or acoustic insulation. Industrially, PUs are produced by copolymerization between polyols and polyisocyanates. Because of the toxicity issues related to the use of isocyanates, there is a need to develop greener and safer route to produce such polymers. This study reports on the synthesis of new sustainable isocyanates-free PU (NIPU) coatings for aluminium anticorrosion. In a first step, bio- and CO2-sourced cyclic carbonates monomers were synthesized by coupling of epoxydized vegetable oils with CO2 using a new efficient bicomponent organocatalyst. In second step formulations including cyclic carbonates/amines/additives were optimized to produce highly adhesive cross-linked NIPU coatings that show good resistance against solvents and long-term barriers preventing the corrosion of the aluminiumsubstrat

Development of Surface Acoustic Wave pressure sensors for monitoring concrete structures

International audienceFor many years surface acoustic waves (SAW) have been used in manufacturing electronic components for industrial and sensing applications. Due to the absence of an embedded electronic system and the possibility of wireless communication this technology can offer a great solution for sensing in harsh environments such as high pressure, temperature and humidity. In the case of refractory concretes, the optimization of the drying cycles has indeed a significant economic impact (reduction of the downtime of the manufacturing lines, energy cost) while making them more efficient and limiting the risks of structural damage. The current sensors on the market are too restrictive on the conditions of use (temperature range, pressure, environment) and therefore do not meet the needs of manufacturers in the refractory concrete sector. Therefore, the objective of the European project named CUBISM, is to fill these gaps by proposing SAW-based pressure sensors capable of operating at much higher temperatures (about 500�C), in wider measurement ranges and in an environment compatible with that of refractory concretes. Developing these types of sensors SAW (Surface Acoustic Wave) consists on choosing the right piezoelectric materials, the optimal IDT (Inter Digital Transducer) configuration and the proper geometry that can withstand these hard conditions. Several prototypes, based on resonators and delay lines have been tested at various temperatures and many pressure levels and the first results show a quite good pressure sensitivity. The results obtained so far will be the subject of this presentation

A quantitative determination of the polymerization of benzoxazine thin coatings by time‐of‐flight secondary ion mass spectrometry

Phenol‐paraphenylenediamine (P‐pPDA) benzoxazines exhibit excellent barrier properties, adequate to protect aluminum alloys from corrosion, and constitute interesting candidates to replace chromate‐containing coatings in the aeronautical industry. For the successful application of P‐pPDA coatings, it is necessary to decrease the curing temperature to avoid the delamination of the coating while preserving the mechanical properties of the alloy, as well as the barrier properties of the coating. However, decreasing the curing temperature leads to less polymerized films, the extent of which requires a quantitative assessment. While the conversion rate of the polymerization reaction is commonly evaluated for bulk samples using differential scanning calorimetry (DSC), a tool for its evaluation in thin films is missing. Therefore, a new approach was developed for that matter using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The relation between the SIMS data integrated from inside thin films and the DSC results obtained on bulk samples with the same curing cycle allowed to calibrate the SIMS data. With this preliminary calibration of the technique, the polymerization of PpPDA coatings can be locally determined, at the surface and along the depth of the coating, using dual‐beam depth profiling with large argon cluster beam sputtering

A quantitative determination of the polymerization of benzoxazine thin coatings by time‐of‐flight secondary ion mass spectrometry

Phenol‐paraphenylenediamine (P‐pPDA) benzoxazines exhibit excellent barrier properties, adequate to protect aluminum alloys from corrosion, and constitute interesting candidates to replace chromate‐containing coatings in the aeronautical industry. For the successful application of P‐pPDA coatings, it is necessary to decrease the curing temperature to avoid the delamination of the coating while preserving the mechanical properties of the alloy, as well as the barrier properties of the coating. However, decreasing the curing temperature leads to less polymerized films, the extent of which requires a quantitative assessment. While the conversion rate of the polymerization reaction is commonly evaluated for bulk samples using differential scanning calorimetry (DSC), a tool for its evaluation in thin films is missing. Therefore, a new approach was developed for that matter using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The relation between the SIMS data integrated from inside thin films and the DSC results obtained on bulk samples with the same curing cycle allowed to calibrate the SIMS data. With this preliminary calibration of the technique, the polymerization of PpPDA coatings can be locally determined, at the surface and along the depth of the coating, using dual‐beam depth profiling with large argon cluster beam sputtering

Impact of industrially applied surface finishing processes on tribocorrosion performance of 316L stainless steel

International audienceThis investigation addresses the effect provided by industrial surface finishes on the tribocorrosion properties of 316L stainless steel exposed to NaCl solution. Three distinct surface treatments were evaluated: passivation (SSO), electropolishing-passivation (SSEP) and micro-undulation (SSM mechano-chemical + electropolishing + passivation). For the tribocorrosion tests, a potentiostatic approach was considered in order to highlight the alloy behavior under two opposite situations, where repassivation of the surface would be thermodynamically possible or not (anodic or cathodic polarization, respectively). The outcomes demonstrated that the surface treatments were either harmful (SSEP) or beneficial (SSM) in terms of resulting tribocorrosion resistance. The specific topography of the micro-undulated sample decreased the real contact area and improved the surface lubrication in aqueous medium. SSEP presented the highest chemical wear and several factors seemed to have contributed for it, including the chemical, mechanical and structural properties of the passive film. Regardless the surface treatment, the tribocorrosion response was modified by the applied potential and more severe damage was determined under anodic polarization. At this potential, calculations of the total surface degradation suggested that volume loss was mainly dominated by chemical wear

The effect of the substrate surface state on the morphology, topography and tribocorrosion behavior of Si/Zr sol-gel coated 316L stainless steel

International audienceIn the present work, a Si/Zr based sol–gel (SG) coating was deposited on 316L stainless steel plates, previously treated by passivation (SSO) or electropolishing (SSEP) producing two different surface states. The SG coatings were compared for SSO and SSEP substrates in terms of morphology, topography and tribocorrosion response. The coating topography revealed a smoother surface for the Si/Zr-SSEP system. The coating deposited on the smoothest surface (Si/Zr-SSEP) presented half of the thickness of the one deposited on the roughest surface (Si/Zr-SSO). Tribocorrosion behavior was studied under potentiostatic control at anodic potential with a continuous recording of current (I) during sliding (pin-on-disc and alumina ball counterbody). Both SG systems showed an increase of current upon 100 sliding contact cycles indicating corrosion activity. After tribocorrosion tests, both systems revealed scratches, typical of abrasion, and coating removal in the wear tracks; the alumina counterparts presented accumulation of wear particles adhered to their surfaces. In conclusion, the initial surface state of the substrate modified the coating thickness, topography but did not significantly alter the tribocorrosion response of the studied SG systems