Corrosion tests produced water systems

A representative production environment for the area of interest, or the most potentially corrosive or highest risk area in a production system, should be duplicated as nearly as possible for all corrosion testing, and its composition should not be altered, except for the purpose of investigating specific field or composition variable, e.g., changes in produced water level, CO2 partial pressure, change in H2S partial pressure (field souring). 

The following discussion applies to corrosion testing of hydrocarbon gas systems, and to the gas phase used for produced/condensed water and crude oil system corrosion testing. 

The following discussion appHes to corrosion testing in produced/condensed water systems and to the liquid water phase used for hydrocarbon gas and crude oil system corrosion testing. 

Microbiological corrosion in the process industries is most often found in three areas cooling water systems, aqueous waste treatment, and gronndwater left in new equipment or piping systems after testing. Nearly all confirmed cases of MIC have been accompanied by characteristic deposits. These are usually discrete mounds. Deposit color can also be an indication of the types of micro-organisnis that are active in the system. For example, iron bacteria deposits on stainless steel, such as those produced by Gallionella, are often reddish. 

Electrochemical tests This group includes the various electrochemical tests that have been proposed and used over the last fifty or so years. These tests include a number of techniques ranging from the measurement of potential-time curves, electrical resistance and capacitance to the more complex a.c. impedance methods. The various methods have been reviewed by Walter . As the complexity of the technique increases, i.e. in the above order, the data that are produced will provide more types of information for the metal-paint system. Thus, the impedance techniques can provide information on the water uptake, barrier action, damaged area and delamination of the coating as well as the corrosion rate and corroded area of the metal. However, it must be emphasised that the more comprehensive the technique the greater the difficulties that will arise in interpretation and in reproducibility. In fact, there is a school of thought that holds that d.c. methods are as reliable as a.c. methods. 

Hydraulic (Liquid Seal) Flame Arresters Hydraulic (liquid seal) flame arresters are most commonly used in large-pipe-diameter systems where fixed-element flame arresters are either cost-prohibitive or otherwise impractical (e.g., very corrosive gas or where the gas contains solid particles that would quickly plug a conventional arrester element). These arresters contain a liquid, usually water-based, to provide a flame barrier. Figure 23-62 shows one design. Realistic tests are needed to ensure performance, as described in EN 12874 [15]. Note that hydraulic flame arresters may fail at high flow rates, producing a sufficiently high concentration of gas bubbles to allow transmission of flame. This is distinct from the more obvious failure mode caused by failure to maintain adequate liquid level. 

The liquid effluent, which consists of water from the evaporator/crystallizer used to produce the solid filter cake produced by the brine-recovery operation, should not pose a significant hazard to human health or to the environment. While the evaporator/crystallizer system has not been tested yet, the composition of the water and solid filter cake can be readily determined from an analysis of the SCWO liquid effluent. As shown in Table 5-10, the liquid effluent is essentially free of organics. The source of the chromium and nickel that were found in some of the effluents is generally believed to be corrosion products from the SCWO reactor components. These elevated levels of metals indicate that the solid filter cake will need to be treated (e.g., by stabilization) prior to disposal in a hazardous waste landfill. 7... 

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