Film formation from phosphates

XPS results show the formation of phosphates, sulphides and oxides on the surface. These observations are similar to those made by Tonck et al. [5], whose studied anti-wear film formation from simple ZDDP systems. In his models, the ferrous substrates were covered with a thin sulphide/oxide layer. This in turn was covered with a thicker phosphate layer. In this paper the model of the film formation (determined from XPS depth profiling), as shown in Figure 6a, shows similar sulphides, oxides and phosphates. 

The (P) L-edge XANES spectra of tribofilms and thermal films generated from the neutral di-isopropyl ZDDP along with the model compounds (zinc metaphosphate and zinc pyrophosphate) are very similar and compare well with model compounds. The surface may also play an important role in catalysis of the thermal decomposition and provide oxygen for phosphate formation. There is also... 

Tribochemically generated tribofilm-phosphorus characterization. Combined results of the phosphorus L-edge and K-edge XANES tribofilm spectra generated from a mixture of MoDTC and ZDDP correspond to medium-chain length polyphosphates. Short-chain polyphosphates were found for thermal antiwear films generated from oil containing MoDTC and ZDDP in various concentrations at 150°C. The XANES spectra clearly show that the counter ion in phosphates is zinc rather than iron. The XANES results do not support the formation of iron phosphate (Kasrai et al., 1998). 

A third class of industrial chemical biocides consists of agents with the ability to inhibit biological film formation, also called surfactants . The term surfactant originates from the phrase surface active agent. Surfactants fall into four broad categories anionic (e.g., soaps, alkyl benzenesulfonates, alkyl sulfonates, alkyl phosphates), cationic (e.g., quaternary ammonium salts), nonionic (e.g., alkyl polyglycosides, alcohol ethoxylates, alkylphenol ethoxylates), and zwitterionic. 

Ion flotation in the presence of surfactants for the treatment of rinses and separation of metal ions is of interest since the sixties [327, 328]. Here, we take only a few examples. The recovery of silver ions from highly diluted solutions is possible by forming a silver-thiourea complex in form of a colloidal precipitate (sublate) followed by sublate flotation with sodium dodecyl benzene sulfonate [329]. Skiylev [330] has developed methods for the removal of non-ferrous metal salts from waste waters. Subject of the investigations were 0.01 - 0.001% solutions of ferrous metal salts. Typical anionic surfactants (alkyl sulfates, alkyl phosphates, alkyl xanthogenates of potassium) or cationic surfactants (quaternary ammonium salts) were used as collectors in ion flotation from diluted solutions. At certain pH, a sublate containing a non-ferrous metal ion was formed, followed by a sublate film formation at the surface due to the rise of the complexes with air bubbles stabilised by the surfactants. 

The XPS and ATR results reported in this work show a good correlation. The chemical analysis of the ZnDTP (pure and dissolved in PAO) thermally decomposed on iron surfaces indicates the formation of zinc polyphosphates. The inorganic phosphates were detected by ATR analysis on the tribological films formed from ZnDTP on iron. XPS spectra acquired on the same samples suggest the formation of iron/zinc orthophosphate and show the presence of metal sulphides in the contact area and inside the wear scar. XPS also provided some evidence that polyphosphates were being formed in the most severely worn regions. 

The improved oxidative stability of phosphated PBI may be due to formation of the benzimidazonium cation (see FIGURE 5). Early work on PBI [8] reported significantly better oxidative stability of PBI films cast from sulfuric acid compared to films cast from organic solvent. Data from other studies fail to support the observation [31]. However, discrepancies may be due to a combined effect of the thermal stability of the PBI salt and the oxidative stability of the PBI cation. PBI sulfate disassociates at temperatures above 350°C whereas PBI phosphate disassociates at temperatures above 850°C. So, a phosphate anion may be able to support a PBI cation to much higher temperatures than a sulfate anion. 

Fortxmati et al. [56] studied PLA/nanocellulose nanocomposite films prepared by twin-screw extrusion followed by a film formation process. Cellulose nanocrystals were synthesized from cellulose microcrystals by sulphuric acid hydrolysis. The crystal surface was modified with surfactant (acid phosphate ester of ethoxylated nonylphenol) as a means to improve the dispersion of filler in PLA matrix. The presence of surfactant... 

Zinc ions inhibit corrosion by a cathodic polarization mechanism based on the precipitation of a zinc hydroxide film at cathodic sites on the metal surface. Zinc in combination with phosphates will lead to a protective film containing zinc phosphate. Film formation is usually rapid due to the low solubility of the zinc compounds at an alkaline pH. The low solubility of zinc in alkaline solutions requires the incorporation of dispersants. The rate of film formation with cathodic inorganic inhibitors should be carefully controlled, as dangerous fouling may occur. Protective films caused by cathodic inhibition are macroscopic and often easily visible, whereas anodic inhibitors generally from very thin, hardly detectable passive films. 

No evidence of anti-wear film formation has been found for totally non-ferrous systems (Al-Si alloy pins on Al-Si alloy plates) from EDX and XPS analysis. This, however, is not the case for systems containing iron (cast-iron pins on Al-Si alloy plates), where traces of phosphates and sulphides are detected from XPS. EDX analysis of these systems does not however detect the P and S, which suggests that the anti-wear film formed was thinner, and hence less stable compared to films formed on ferrous systems (Figure 6b). 

Uranium may be deposited electrolytlcally at the cathode of a cell from acetate,carbonate, 22. oxalate, formate,- 22. phosphate, fluoride,and chloride — solutions. Many of the uranium electrodeposition procedures have been developed In an effort to prepare thin, uniform films for alpha and fission counting rather than to separate the element from any particular Impurity. However, In the work of Smith and co-workers and Coomans uranium was separated from alkali and alkaline earth metals and zinc. Oasto and Rodden and Warf— review much of the material pertinent to the electrodeposition of uranium. 

Very interesting behavior of incorporating anions can be observed when a multicomponent electrolyte is used for oxide formation. Here, anion antagonism or synergism can be observed, depending on the types of anions used. The antagonism of hydroxyl ions and acid anions has been observed in a number of cases. Konno et a/.181 have observed, in experiments on anodic alumina deterioration and hydration, that small amounts of phosphates and chromates inhibit oxide hydration by forming monolayer or two-layer films of adsorbed anions at the oxide surface. Abd-Rabbo et al.162 have observed preferential incorporation of phosphate anions from a mixture of phosphates and chromates. 

ZDDP decomposes by a number of routes involving free radical and redox processes. Film composition varies from the iron-rich bonding layer, through the zinc phosphate layer to the outer surface, which contains organic material incompletely converted to precursor species. The polyphosphate chain length may vary as a function of depth into the film and the conditions under which the film is formed. Formation of polyphosphate tribofilms from simple ZDDP solutions is promoted by self-association of ZDDP molecules, which increases the local concentration of ZDDP. 

---