Influence of modification time and high frequency ultrasound irradiation on self-assembling of alkylphosphonic acids on stainless steel: Electrochemical and spectroscopic studies

Abstract

Self-assembly of alkylphosphonic acids on stainless steel was investigated under different conditions. Four different alkylphosphonic acids exhibiting alkyl chain of various size were synthesized and studied: butylphosphonic acid (C4P), octylphosphonic acid (C8P), decylphosphonic acid (C10P), and hexadecylphosphonic acid (C16P). Electrochemistry experiments were extensively carried out in order to determine electrochemical surface blocking of adsorbed layers in function of grafting time. In term of surface blocking, an 8h modification time was optimal for all alkylphosphonic acids. Longer immersion times lead to degradation of adsorbed layers. For the first time, grafting of C16P was studied under high frequency ultrasound irradiation. Interestingly, grafting process is highly accelerated under sonication and well-covering C16P modified substrates are obtained after 1h of immersion under ultrasound irradiation. This would allow to elaborate high-quality alkylphosphonic acids modified samples within much shorter times. Water contact angles measurements and X-ray Photoelectrons Spectroscopy (XPS) confirmed presence of adsorbed alkylphosphonic acids on stainless steel surface. A very tight link between electrochemical blocking, surface hydrophobicity and species chemical grafting was established.

Organic corrosion inhibitors: where are we now? A review. Part IV. Passivation and the role of mono- and diphosphonates

“…The first of these includes works in which the protective properties of APhs with a relatively small alkyl length, C 7 -C 10 , were studied, which made it possible to obtain their thin layers, including SAMs, in aqueous solutions [16][17][18][19][20][21][22][23][24][25][26]. In the second group more hydrophobic monophosphonic compounds were studied, mainly octadecylphosphonic acid (APhC 18 ), that cannot be applied from aqueous solutions [27][28][29][30][31][32][33]. The APhs from the first group adsorbed from aqueous solutions form protective layers on iron surface, which can suppress the dissolution of the metal and stabilize its passive state.…”

“…Recently, in another work [28] the influence of the processing time of 304L stainless steel by ethanol solutions of 5.0 mM APhC 4 , APhC 8 , APhC 10 or APhC 16 was studied in order to determine the optimal conditions for the formation of SAM. It was found that the best results, judging from the cyclic voltammetry curves recorded in an aqueous solution containing 0.2 M Na 2 SO 4 and 5 mM K 4 [Fe(CN) 6 ], were obtained at 8 h in APh solutions.…”

Effect of cavitation intensity control on self-assembling of alkanethiols on gold in room temperature ionic liquids

“…The affinity between the reactive group and the substrate is of prime importance for ensuring efficient chemisorption on the surface. Many types of SAMs exhibiting various reactive headgroups (thiols [6] , phosphonic [7] , [8] , carboxylic [9] , [10] ) have been grafted on gold [11] , titanium [12] , copper [13] or stainless steel [14] to name just a few.…”

“…between 16 and 24 h, which renders industrial applications very difficult. In an attempt to solve this problem, some studies on the use of ultrasound to accelerate SAM grafting process have been carried out [11] , [14] , [18] , [19] , [20] . The studies by Atobe et al .…”

“…They also studied self-assembling of alkylphosphonic acids on stainless steel under high frequency ultrasonication. They reported an increase in layer formation process under sonication: 1 h under irradiation to obtain a coating of good quality compared with 8 h in silent conditions [14] . In all these studies, cavitation activity was claimed to be the main cause for these kinetics increases and enhanced SAM organizations.…”