This standard recommended practice describes the use of iron counts as a corrosion-monitoring method and some common problems encountered when using this method. For several years, NACE Task Group T-1C-7 on Iron Determination examined the problems and successes experienced by oil-producing companies and service companies using iron counts as a corrosion monitor and determined that iron counts on wellhead samples can provide information on the existence of downhole corrosion and the effectiveness of inhibitor treatments. Iron counts can also give information on the corrosion activity in flowlines in waterflood systems and oilproduction operations. This standard is a guide for those designing corrosion-monitoring programs as well as those carrying out the programs in the field.

This standard was originally prepared in 1992 by Task Group T-1C-7, a component of Unit Committee T-1C on Detection of Corrosion in Oilfield Equipment. T-1C was combined with Unit Committee T-1 D on Corrosion Monitoring and Control of Corrosion Environments in Petroleum Production Operations. This standard was revised by Task Group T-10-55 in 1998, and is issued by NACE International under the auspices of Group Committee T-1 on Corrosion Control in Petroleum Production.

1.1 The anomalies experienced when using iron counts as a monitor for corrosion result mostly from the varying, usually uncontrollable, conditions found in almost every production system. Because the term iron count refers to the concentration of iron dissolved in the water expressed as milligrams per liter (mg/L) or ppm (mg/kg), those monitoring corrosion using iron counts must specify whether the iron content is based on the total fluid produced and whether the iron is reported as soluble iron, ferrous iron, or total iron. The exact method of sampling and sample treatment required to separate and analyze for ferrous, ferric, soluble, and total iron content of a water sample is described in the analytical procedures cited in the Reference section. If techniques are employed to analyze for the individual species of iron, the final report must indicate the form of iron being reported. If only the typical total acid-soluble iron content is determined, the final report should indicate that the result is "total iron." The usual oilfield iron count is total iron content of an acid-treated sample. In order to use iron counts to monitor corrosion trends, the same species must be determined consistently for a given sampling point in a system. For comparison of systems producing varying amounts of water, a more meaningful tool is the iron production rate that takes into consideration the water flow rate at the time of sampling. The iron count is converted to an iron production rate, usually expressed in kilograms of iron per day (kg/day [lb/day]).

Historical Document 1998