Ohio University

Naphthenic Acid Joint Industry Project

Project Development

Naphthenic acids corrosion represents an important challenge for the oil refining industry when low-quality crude oils are processed. The corrosivity of low-quality crudes is caused mainly by their natural naphthenic acids (NAP) and sulfur content which becomes particularly problematic at high-temperature and high-velocity conditions, typical for distilling towers, furnaces, and transfer lines, causing important material losses during processing. Understanding and reducing the corrosive effects of NAP became the main focus for numerous research studies over the past decade, done both in the oil and gas industry and in academia as well.

In 2004, the Institute started a research program sponsored by a major oil and gas company focusing on naphthenic acid and sulfur corrosion and on factors like high temperature and flow that influence this corrosive processes. The project continued for six years and investigated the complex relationships between NAP and sulfur-containing compounds in oil fractions using different experimental apparatus and analytical instruments. Based on the knowledge accumulated in six years of experimental and analytical work, the Institute decided to continue this research project as a Joint Industry Project (NAP JIP) opened to any company interested in “downstream” corrosion. NAP JIP started in January 2011, was supported financially by 11 companies (oil and gas companies and companies related to the oil industry), and ended in June 2014.

NAP JIP 2 continues for three more years the successful work of NAP JIP. It started in July 2014, will end in 2017, and it is financially supported by most of the initial sponsors of the first phase of this research project.

NAP JIP 2 Objectives

Naphthenic acid and sulfur corrosion are two interconnected and complementary processes that take place in refineries processing low-quality crudes. It is common knowledge that iron sulfide, the by-product of sulfur corrosion builds on metal surfaces offering limited protection against naphthenic acid attack. Recent studies indicate that the scale built on metal surfaces when oils are processed has a more complex composition including also metal oxides besides the iron sulfide. Based on these studies and on experimental results generated in the NAP JIP, it appears that the metal oxide layer also affects corrosion. NAP JIP 2 proposes further experimental work aimed at generating a better understanding of the mechanism of naphthenic acid corrosion and its interaction with sulfur-containing compounds. Therefore the objectives of the new project phase are:

  • Investigating the role of naphthenic acids and sulfur compounds in the process of protective scales formation
  • Evaluating the scale protectiveness against naphthenic acid attack in single-phase flow and in two-phase flow systems.
  • Incorporating all-new findings and experimental results of these tests in an upgraded version of the mechanistic model of naphthenic acid corrosion, previously generated in the project's first phase.

The experimental work of NAP JIP 2 is executed at the Institute on different experimental units specialized for studying NAP acid corrosion under experimental conditions designed to be as close to refinery operating conditions as practical. This equipment is capable of specialized experiments at high temperature under either static conditions – stirred autoclaves or continuous flow conditions in single-phase flow or two-phase flow loops.

The analytical work is performed also in our Institute using the Scanning Electron Microscope (JEOL JSM-6390) coupled with an Energy Dispersive X-ray Spectrometer (SEM/EDS), the InfiniteFocus Profilometer Microscope (IFM), or the Atomic Force Microscope (AFM). For chemical analysis of gaseous compounds NAP JIP 2 uses a Micro-GC (Varian 490-GC PRO Micro-GC) and for TAN evaluations according to ASTM D664 the project uses a Micro TAN Titrator (Aquamax Micro TAN).


  • A thorough characterization of NAP acid and sulfur compounds role in scale formation from crude fractions at high temperatures.
  • An evaluation of different types of steel tested with different fractions at high temperatures using a specific testing protocol.
  • Full reports delivered every six months including experimental data, their analysis, and discussion.
  • A searchable lab database on naphthenic acid corrosion results which will be available to the sponsors and used to improve the predictive model.
  • An improved version of a mechanistic predictive model of naphthenic acid corrosion including the latest experimental results.

Please contact Gheorghe Bota for more information on the NAP Project.