Search results

The purpose of this paper is to investigate the resistivity of geopolymer cement with nano-silica additive toward acid exposure for oil well cement application.

An experimental study was conducted to assess the acid resistance of fly ash-based geopolymer cement with nano-silica additive at a concentration of 0 and 1 wt.% to understand its effect on the strength and microstructural development. Geopolymer cement of Class C fly ash and API Class G cement were used. The alkaline activator was prepared by mixing the proportion of sodium hydroxide (NaOH) solutions of 8 M and sodium silicate (Na₂SiO₃) using ratio of 1:2.5 by weight. After casting, the specimens were subjected to elevated curing condition at 3,500 psi and 130°C for 24 h. Durability of cement samples was assessed by immersing them in 15 wt.% of hydrochloric acid and 15 wt.% sulfuric acid for a period of 14 days. Evaluation of its resistance in terms of compressive strength and microstructural behavior were carried out by using ELE ADR 3000 and SEM, respectively.

The paper shows that geopolymer cement with 1 wt.% addition of nano-silica were highly resistant to sulfuric and hydrochloric acid. The strength increase was contributed by the densification of the microstructure with the addition of nano-silica.

This paper investigates the mechanical property and microstructure behavior of emerging geopolymer cement due to hydrochloric and sulfuric acids exposure. The results provide potential application of fly ash-based geopolymer cement as oil well cementing.

Inhibiting acids Hydrochloric acid solution POLYRAD 0515A and 1110A manufactured by Hercules Powder Co. Ltd. have received wide acceptance as corrosion inhibitors for use in hydrochloric acid solution. This acid, in common with other industrial acids, will corrode iron and steel vessels during processing unless they are protected by the presence of a suitable inhibitor. In the case of hydrochloric acid, a number of processes such as metal cleaning, metal pickling and oil well acidifying operations necessitate the use of a soluble, heat‐stable inhibitor in the acid solution.

This concluding part reviews the actions of inhibitors to acidic, ammonical, organic, atmospheric and miscellaneous product corrosion on aluminium. The comprehensive reference list is also concluded.

To investigate the inhibitive effect of Delonix regia extracts to reduce the corrosion rate of aluminium in acidic media. The study was a trial to find a low cost and environmentally safe inhibitor to reduce the corrosion rate of aluminium.

The inhibition efficiency was evaluated using the hydrogen evolution technique at 30°C. The mechanism of adsorption inhibition and type of adsorption isotherm was characterised from trends of inhibition efficiency and kinetic data.

Delonix regia extracts inhibited the corrosion of aluminium in hydrochloric acid solutions. The inhibition efficiency increased with increasing concentration of the inhibitor but decreased with increase in exposure time. The acid extracts (hydrochloric acid seeds extract (HSE) and hydrochloric acid leaf extract (HLE)) were found to be more effective than the ethanolic extracts (ethanol seeds extract (ASE) and ethanol leaves extract (ALE)) and the inhibition followed the order: HSE (93.6 per cent) > HLE (83.5 per cent) > ASE (63.9 per cent) > ALE (60.4 per cent). The low negative values of ΔG_ad: −20.14 kJ mol⁻¹ for HSE, −18.08 kJ mol⁻¹ for HLE, −15.96 kJ mol⁻¹ for ASE and −15.12 kJ mol⁻¹ for ALE, as calculated from the Langmuir isotherm, indicated that the inhibitor molecules adsorbed onto aluminium by a physiosorption‐based mechanism. A first‐order type of reaction mechanism was obtained from the kinetic treatment of the H₂ gas evolution data.

Further investigations involving electrochemical studies such as polarization method should shed further light on the mechanistic aspects of the corrosion inhibition.

This paper provides new information on the possible application of Delonix regia as an environmentally friendly corrosion inhibitor under the specified conditions. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

The purpose of this paper is to observe the colour and thermal stability of natural red dye consisting of anthocyanin with addition of different aqueous acids and applied as coating films.

The natural red dye was extracted from Hibiscus sabdariffa L. (roselle) flowers and mixed with 1 per cent hydrochloric acid, 5 per cent acetic acid, 5 per cent citric acid and 5 per cent oxalic acid. All the dye samples were exposed to heat and UV-B to observe the colour stability by calculating the half-life and rate of reaction. In coating film application, each of the dye samples was mixed with 25 wt% of poly(vinyl alcohol) (PVA) and applied on to a glass substrate. The coating samples’ colour stability was observed by using CIE L*a*b* colour space coordinates. The coating films’ weight loss stability against temperature was observed by using thermogravimetric analysis.

Addition of hydrochloric acid enhances the thermal and UV stability of the anthocyanin natural dye. This can be observed from the calculation of the half-life of the dye. The half-life values for the thermal and UV stability studies were 1,155 hours and 210 hours, respectively. In coating films, the sample with addition of acetic acid showed the highest colour stability with colour difference (ΔE*) value 8.95.

The coating films developed in this work are not suitable to be applied on metal substrates due to the presence of water, which can contribute to the corrosion formation.

The coating films developed in this work are suitable for washable coating application. In other words, they are non-permanent coatings applied on a glass substrate.

Development of water-based coatings from PVA binder with anthocyanin colourant is introduced in this study.

In British industry alone, the cost of corrosion is estimated at over £1,000 million annually. A high proportion of this cost is caused by two of the most widely used—and corrosive—industrial chemicals: sulphuric and hydrochloric acids. Yet the corrosive damage caused by these two chemicals can be controlled and often eliminated by correct selection of construction materials. In the chemical and allied process industries many companies have been using glass reinforced plastic equipment to handle these two acids for a number of years with excellent results. Yearly, the number of reported applications increases as experience widens and fabrication techniques become more advanced.

Sulphates, chlorides, nitrates and oxidising agents were studied as impurities in sulphuric acid and hydrochloric acid. Presence of chlorides inhibited the dissolution of mild steel in sulphuric acid whereas presence of nitrates and oxidising agents accelerated the reaction. In the case of hydrochloric acid, mild steel dissolution was inhibited by sulphate impurities and was accelerated by nitrates and oxidising agents. Ipomoea and Amaranthus (5%) were used as inhibitors. Both of them showed good performance in the two acids in the presence of impurities.

Anode weight loss and polarization studies of brass in nitric, hydrochloric and sulphuric acids indicate that the copper dissolves in the cuprous state in hydrochloric acid whereas it is in cupric form in the other two acids. In nitric acid the local cell corrosion is completely stopped, when made sufficiently anodic showing a positive difference effect.

Much progress has been made in the field of corrosion technology in the last few years and many new corrosion‐resisting materials have been developed, including improved types of plastics and metals such as zirconium, titanium and tantalum. Plastics are finding extensive use as lining materials for chemical plant operating at moderate temperatures, but the poor thermal conductivity of most plastics makes them unsuitable for the transfer of heat. The recently developed metals and their alloys are extremely expensive to produce and fabricate and, so far, their use has been confined to certain specialised applications, although full‐scale production of zirconium is being carried out in America, mainly because of the low capacity of the metal for absorbing thermal neutrons. At the moment, however, these metals, because of their high cost, cannot compete commercially on a large scale with the older well‐established corrosion‐resisting alloys such as the high‐silicon iron alloys. The excellent corrosion resistance of the high‐silicon iron alloys, even at high temperatures, and their high thermal conductivity have established them as almost standard alloys for acid concentration and cooling plant construction. The following article outlines their composition and properties.

“Metals are attacked by acid” is a commonly‐heard statement that is reasonably correct but rather too sweeping. Some metals are “noble” in that they are not affected by ordinary, non‐oxidising acids such as hydrochloric acid, and the important noble metals in electronics are copper, silver, gold, palladium and platinum. Many metals are highly reactive, but cover themselves with an inert, self‐repairing layer of oxide when exposed to air. These include tantalum, titanium, stainless steel and aluminium. The oxide films vary widely in their resistance to the hydrochloric acid produced by burning PVC, with tantalum oxide remaining inert under all conditions and titanium oxide being attacked only by boiling, concentrated acid. The chromium oxide inert film on stainless steel, and the alumina film on aluminium react readily, giving the chloride salts of the metals and water: