Corrosion inhibitors application

The history of corrosion inhibitors and neutralizers and their invention, development, and application in the petroleum industry is documented by a review of Fisher [605]. Early corrosion inhibitor applications in each of the various segments of the industry, including oil wells, natural gas plants, refineries, and product pipelines, are reviewed. 

FIG. 12—The logic diagram for new field corrosion testing to determine the Corrosion Rate Break produced water level for carbon or low alloy steel corrosion, corrosion Inhibitor application, and corrosion resistant ailoy selection. 

The relationship between a corrosion product layer and inhibitors has also been discussed, among others, by Lorenz [66], and Lorenz and Mansfeld [67]. These authors point out that in many practical systems, for instance aerated water and carbon steel, an interaction occurs between, in this case, iron oxide and the inhibitor to the point where the inhibitor is not only adsorbed on the oxide surface, but actually incorporated into the three-dimensional oxide layer. Clearly, three-dimensional or interphase inhibition caimot be achieved in short tests or by filming procedures. Furthermore, measuring techniques have to take into consideration the altered chemical and electrochemical conditions across such bulk interphase layers. It is unfortunate that this aspect of corrosion and corrosion inhibition has not received more attention, and it is suggested that this lack of attention has seriously held back all aspects of corrosion inhibitor applications and monitoring of effectiveness. 

Miscellaneous Commercial Applications. Dimer acids are components of "downweU" corrosion inhibitors for oil-drilling equipment (see Petroleum Corrosion and corrosion inhibitors). This may account for 10% of current dimer acid use (71). The acids, alkyl esters, and polyoxyalkylene dimer esters are used commercially as components of metal-working lubricants (see Lubrication). Dimer esters have achieved some use in specialty lubricant appHcations such as gear oils and compressor lubricants. The dimer esters, compared to dibasic acid esters, polyol esters and poly(a-olefin)s, are higher in cost and of higher viscosity. The higher viscosity, however, is an advantage in some specialties, and the dimer esters are very stable thermally and can be made quite oxidatively stable by choice of proper additives. 

Separate the metal from the environment with a physical barrier. Many corrosion inhibitors make use of this principal to protect metals. Proper use of an appropriate inhibitor may reduce or eliminate pitting. Pits are frequently initiation sites for corrosion-fatigue cracks. The effectiveness of inhibitors depends upon their application to clean metal surfaces. An example of this method is the use of zinc coatings on steel to stifle pit formation. 

Application of Corrosion Inhibitors. There are basically two main techniques used to apply corrosion inhibitors in drilling operations. In the first method inhibitors are added to the drilling fluid system either by mixing the additives through the rig s chemical hopper or through additions into the mud pit. The treatment can be achieved in two ways, batch treatment or continuous treatment. In some cases it may be necessary to use both types of treatment simultaneously. The second technique of applying is directly coating the corrosion inhibitors on the drillpipe. 

Whatever method of inhibitor application is used, care must be taken to maintain optimum concentration of the corrosion inhibitor. In the event of addition of makeup water or untreated reserve fluids to maintain other fluid properties, care must be taken to ensure the addition of the correct amounts of corrosion inhibitors. 

An understanding of the basic principles of the science of metallic corrosion is clearly vital for corrosion control, and as knowledge of the subject advances the application of scientific principle rather than an empirical approach may be used for such purposes as the selection of corrosion inhibitors, formulation of corrosion-resisting alloys, etc. 

The principles and practice of corrosion inhibition have been described in terms of the factors affecting inhibitor performance and selection (principles) and the more important practical situations in which inhibitors are used (practice). For the latter a brief account is given of the nature of the system, the reasons for inhibitor application and the types of inhibitor in use. 

Since corrosion inhibitors are used in a wide range of applications, no universal test method exists. Recognised methods tend to relate to a product or process in which the inhibitor forms a part rather than to the inhibitor per se. Thus, tests exist for inhibited coolants, cooling waters, cutting oils, pickling liquids, etc. 

Anodic polarization also may occur. Typically, this begins with the formation of a thin, impervious oxide film, chemisorbed at the anode (as on the surface of stainless steels). However, for most metals used in boiler plant systems this chemisorption process must be aided by anodic corrosion inhibitors to reduce corrosion rates to tolerable levels. An example is the application of nitrite-based inhibitors, widely used in HW heating systems. 

Alkalinity boosters, which are vitally necessary to enable carbonate, phosphate, balanced polymer (polymer plus phosphate or chelant), and some other program types to function, are perhaps best described as conjunctional treatments, whereas oxygen scavengers, antifoams, and condensate line corrosion inhibitors are adjuncts. Programs such as phosphate-tannin mixtures are sometimes described as adjunct treatments. The chemistries and applications of various types of conjunctional treatments and adjuncts are described in this chapter. 

These same diamine materials find further application in, for example, formulations for mussel and barnacle control in large once-through, condenser cooling systems, as corrosion inhibitors and biostats for hydrostatic testing of oil and gas pipelines, and as corrosion inhibitors in food industry retort cookers. 

Gandhi, Ashish (Cortec Corporation). Volatile Corrosion Inhibitors Unique Water Treatment Applications. The Analyst, Journal of the Association of Water Technologies, USA, Fall 2000. 

A survey of applications was also done by Czichocki et al. [73], including such applications as inks and paints, paper, photography, plastics, emulsion polymerization, pharmaceuticals, flotation, corrosion inhibitors, lubricants, electroplating, electrophoresis, and catalysts for ethoxylation. 

This pump is the same in principle as the piston type but differs in that the gland is at one end of the cylinder making its replacement easier than with the standard piston type. The sealing of piston and ram pumps has been much improved but, because of the nature of the fluids frequently used, care in selecting and maintaining the seal is very important. The piston or ram pump may be used for injections of small quantities of inhibitors to polymerisation units or of corrosion inhibitors to high pressure systems, and also for boiler feed water applications. 

Metalworking fluids contain mineral oils (refer to p. 80) or synthetic lubricants they are used neat or in admixture with water. They may contain small amounts of biocides, stabilizers, emulsifiers, corrosion inhibitors, fragrances and extreme pressure additives. The formulations render them suitable for application to metal being worked, generally from a recirculatory system, to provide lubrication, corrosion protection, swarf removal and cooling of the tool and machined surface. 

A fully automated instrumental procedure has been developed for analyzing residual corrosion inhibitors in production waters in the field. The method uses ultraviolet (UV) and fluorescence spectrophotometric techniques to characterize different types of corrosion inhibitors. Laboratory evaluations showed that fluorescence is more suitable for field application because errors from high salinity, contamination, and matrix effect are minimized in fluorescence analysis. Comparison of the automated fluorescence technique with the classic extraction-dye transfer technique showed definite advantages of the former with respect to ease, speed, accuracy, and precision [1658],... 

These are usually mineral oils or synthetic basestocks containing a complex mixture of additives including corrosion inhibitors, extreme pressure additives and emulsifiers. They are almost exclusively oil-in-water emulsions, although in rare instances, invert emulsions may be used. They are normally used between l%-20% emulsions depending on the application. As these products are water extendible, they are subject to attack by micro-organisms. As a consequence, they are often formulated with one or more preservatives. 

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