Acetylenic alcohols as inhibitors of iron acid corrosion. Improvement of the inhibition efficiency of a class of substances based on their action mechanism

Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) is an environmental friendly biocide commonly used in oil fields. It also has been used to control iron sulfide precipitation for water injection and to remove deposits in oil production systems. In this study, THPS was examined as the dissolver for scale deposits formed on downhole tubular of high temperature sour gas wells. These deposits consisted of a wide range of mineral phases and are often dominated with various forms of iron sulfides and iron oxyhydroxides. The THPS based dissolvers were studied at various concentrations, pH values and with different additives. These additives included ammonium chloride, chelating agents and phosphonates. Experimental results indicated that the dissolving power was not proportional to THPS concentration. The maximum dissolution was observed in THPS concentration of 25 to 50%, depending on scale composition. Its dissolving power could be significantly increased with both ammonium chloride and chelating agents. The synergistic effect of ammonium chloride was largely attributed to pH decrease. As a result, the corrosivity of THPS solution to metallurgy was increased with the addition of ammonium chloride. The corrosion rate of mild steel was increased over three times with 4% ammonium chloride added. Contrary to previous reports, phosphonate additives decreased scale dissolution and induced new precipitation. Formation of calcium sulfate precipitates was also observed during dissolution of calcite, which will limit the THPS from scales containing calcium carbonate. This study also revealed the dissolution behavior of different minerals in the THPS solution. Iron oxyhydroxides had the highest dissolution rate, followed by calcite, siderite and pyrrhotite. Pyrite, marcasite and anhydrite were almost insoluble in the tested solutions. Results from this study can be used as guideline for the development and design of THPS based scale dissolvers.

Section: Introductionmentioning

confidence: 99%

Laboratory assessment of tetrakis(hydroxymethyl)phosphonium sulfate as dissolver for scales formed in sour gas wells

Wang¹,

Shen²,

Badairy³

et al. 2015

“…However, there are cases where besides CI chemisorption that allows it (or its fragment) to hold firmly to the metal surface, an important role is played by deep chemical transformations of adsorbate particles that lead to structuring of the protective film and make it more resistant to a corrosive environment. The CIs of this kind include some acetylenic alcohols that are long known for their efficiency in acid solutions even at t > 100°C [18][19][20][21]. Unfortunately, they are very toxic and a search for their replacement is very relevant.…”

Section: Adsorption Of Corrosion Inhibitors On Metals and Passivationmentioning

confidence: 99%

Progress in the science of corrosion inhibitors

Kuznetsov

pr.²,

Moscow³

et al. 2015

The physicochemical features of corrosion inhibition of metals (alloys) strongly depend on the composition of the corrosive environment, its pH, temperature t, hydrodynamic conditions, the chemical nature of the metal to be protected, and the state of its surface, the presence of oxides, dirt, or corrosion products on it. This "multifactor" nature of corrosion seriously complicates the theoretical choice of an efficient corrosion inhibitor (CI), often requiring careful experimental studies and creating unjustified skepticism about the fundamental character of the physical chemistry area related to the study and development of CIs. Meanwhile, this skepticism can be proved wrong by the progress made over the past quarter century in various subareas. Key words: corrosion inhibitors, adsorption, metal passivation, volatile corrosion inhibitors, migrating inhibitors, local depassivation of metals, protecting coatings. Adsorption of corrosion inhibitors on metals and passivationAdsorption on a protected surface is the first event that often determines CI efficiency. Difficulties of its measurement in situ are caused by dissolution and/or oxidation of the metal substrate with time. The uncertainty in separating the effects of adsorption and changes of the state of the metal surface often does not permit to unambiguously interpret the results obtained, for example, by electrochemical impedance spectroscopy (EIS) or using radioactive tracers. In his first "Inhibitors of corrosion of metals in neutral media" (1953), I.L. Rozenfel'd considered only inorganic CIs. He remained interested in these inhibitors throughout his whole life, so it is not surprising that in his latest book "Corrosion Inhibitors" (1977) he reexamined the interaction of some inorganic CIs, primarily chromate, with the metal at a more modern level, including a quantum-chemical approach. However, studies on the

“…Electrochemistry is a powerful tool to study corrosion phenomena and widely applied in academic and industrial research [11][12][13][14]. Therefore, this method was chosen for this study.…”

Section: Corrosion Testingmentioning

confidence: 99%

The influence of alkalising amines on the film formation by oleyldiamine

Hater¹,

Kraft²,

Foret³

2015

The film formation of film forming amines (FFAs), commonly used as corrosion inhibitors in water/steam cycles, has been subject of various studies. However, less is known of the impact of alkalising amines (AA) on the film formation. AAs have a solubilising effect on the FFA and as a consequence might indirectly influence the properties of the film.Therefore, the film formation of oleyldiamine, a commonly used FFA, on carbon steel has been studied with electrochemical impedance spectroscopy (EIS) in defined test water, containing 200 mg L -1 of NaCl, with and without the presence of different AAs. The studies have been carried out at two different pH values over an exposure time up to 5 h.All EIS spectra of the blank show one semi-circle, whereas two distinct semi-circles have been observed in the spectra of the test solutions with FFA. Therefore, the steel solution interface has been described by two different equivalent circuits using resistances and constant phase elements. All EIS spectra could be fitted with good agreement to the experimental data. The spectra showed significant and systematic changes throughout the exposure time.All polarisation resistances measured with FFA at pH 9.0 are much higher compared to the data obtained at pH 8.2. The polarisation resistance of the blank solution is strongly decreasing over time following roughly an exponential law and almost comes to a steady state after 5 hours. In contrast to this the solutions containing FFA show a linear increase of the polarisation resistance over time. Obviously the film formation has not yet completely been finished within the experimental period.The FFA solutions containing the two different AA show a similar behaviour over time and almost the same high polarisation resistance, reflecting the excellent corrosion protection. Overall, the data indicate that the film obtained with oleylamine in the solutions containing DEAE provides a slightly better protection than FFA solution with CHA. Thus, the more toxic CHA can be replaced by DEAE.