Abstract
This paper will present a detailed study on corrosion current and corrosion behavior using electrochemical technique. The corrosion rates of different alloys and metals in a test liquid of blow down water collected from an oil field boiler were measured. The working electrode was made from the alloy/metal material using a cold mount epoxy and the corrosion rates of the alloys/metals were compared. The effects of a corrosion inhibitor and pH value on the corrosion behavior were investigated. The electrochemical method provided reproducible test results and a time efficient way for corrosion rate measurement.
Introduction
Knowledge of alloy corrosion rates at facilities is very critical for decision making such as evaluating the lifetime of water pipelines made of alloys, determining the value of installing internal coatings, adding a corrosion inhibitor to the liquid system, etc. There are different methods available for measuring the corrosion rates of alloys.
Of all the methods, mass loss1 and electrochemical techniques 2,3 can both be used in laboratories to help end users predict corrosion rates of the candidate alloy materials that may be used for their facilities. Electrochemical method has been accepted by ASTM standards. 4,5 Mass loss involves immersion of alloy material in a field liquid for the test duration as long as possible, followed by removing only the corrosion product on test coupons. The corrosion rate will be estimated by the weight loss over the test duration. With electrochemical method, only a few hours will be required to determine the corrosion rate of an alloy.
Although organic coatings are being extensively used to protect tanks, vessels, pipes, structural steels, etc. from corrosion, coatings are not the option in some situations due to limitations. For example, coating applications are not easily carried out in small diameter (1.5 inch internal diameter and below) pipes and inside valves. For some high temperature (>150°C) applications, very rarely can organic coating perform well. The coating may detach due to the high temperature and clog the piping system.
