headerdrawing1.jpg (96365 bytes)

Sulphuric Acid on the WebTM Technical Manual DKL Engineering, Inc.

Knowledge for the Sulphuric Acid Industry Line.jpg (1139 bytes)

Sulphuric Acid on the Web

Introduction
General
Equipment Suppliers
Contractor

Instrumentation
Industry News
Maintenance
Acid Traders
Organizations
Fabricators
Conferences

Used Plants
Intellectual Propoerty
Acid Plant Database
Market Information
Library

Technical Manual

Introduction
General

Definitions
Instrumentation
Plant Safety
Metallurgial Processes
Metallurgical
Sulphur Burning
Acid Regeneration
Lead Chamber
Technology
Gas Cleaning
Contact
Strong Acid
Acid Storage
Loading/Unloading

Transportation
Sulphur Systems
Liquid SO2
Boiler Feed Water
Steam Systems

Cooling Water
Effluent Treatment
Utilities
Construction
Maintenance
Inspection
Analytical Procedures
Materials of Construction
Corrosion
Properties
Vendor Data

DKL Engineering, Inc.

Handbook of Sulphuric Acid Manufacturing
Order Form
Preface
Contents
Feedback

Sulphuric Acid Decolourization
Order Form
Preface
Table of Contents

Process Engineering Data Sheets - PEDS
Order Form
Table of Contents

Introduction

Bibliography of Sulphuric Acid Technology
Order Form

Preface
Contents

Sulphuric Acid Plant Specifications
 

Google Search new2.gif (111 bytes)

 

log 2.JPG (76785 bytes)

Sharplex.jpg (28953 bytes)

MAHLEInd.jpg (21078 bytes)

 


Corrosion
June 6, 2005

Introduction
Carbon Steel
Corrosion Charts
Associated Links

Introduction

The moment process gases or liquids are introduced to the plant, corrosion begins and the plant starts its slow but sometimes fast decline.   Selecting the correct materials of construction is the best method of slowing the progress of corrosion.  In order to select the correct material the designer and operator of an acid plant must know how a particular material will withstand exposure to the process conditions.

Back to top

Carbon Steel

Although the overall corrosion rate of carbon steel in concentrated sulfuric acid service is low, some corrosion still occurs.  The reaction products from the corrosion process are iron sulfate and hydrogen gas.

Fe + H2SO4 -> FeSO4 + H2

This reaction can be considered as the sum of two different reactions occurring at different sites on the metal surface:

Fe -> Fe++ + 2e- (oxidation)

2H+ + 2e- -> H2 (reduction)

The iron sulphate film is relatively weak and can be disturbed by high acid velocities or other disturbances in the liquid.

Hydrogen gas can be a problem with carbon steel in sulphuric acid environments because it can literally scrub off the mechanically weak iron sulphate film, which is the only thing protecting the steel from attack.

During periods of normal flow, the gas bubbles are very small and evenly distributed, and they are quickly carried downstream along with the acid, generally without causing a problem to the pipe wall.  However, when acid flow stops, the gas bubbles accumulated along the pipe wall in the upper half of the pipe. When the flow resumed, the hydrogen gas bubbles are dislodged and rise to the very top of the pipe, scrubbing off the protective film along the way. With the film gone along the top of the pipe, the surface corroded very quickly until the iron sulphate film reforms.

Repeating this process over and over again results in a pattern of curved grooves in the top half of the pipe, all radiating toward a central longitudinal groove at the very top.

Although we're usually not privileged to see such an excellent example of hydrogen grooving, it's not an uncommon occurrence in sulfuric acid service, particularly under upset conditions. To guard against it, the usual recommendation is to use very thick steel, in recognition of the possibility of localized corrosion, and to keep the average velocity in pipes below 3 ft/sec to reduce the scrubbing effect of any hydrogen bubbles that do form.

Back to top

Corrosion Charts

Corrosion charts are one source of information that will help identify the correct material of construction for a particular application.

Material Description Source
254 SMo Isocorrosion Curves
Corrosion Rate = 0.1 mm/y (4 mpy)
0-50% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
Naturally Aerated, Corrosion Rate = 0.1 mm/y (4 mpy)
0-100% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
0-100% H2SO4, 200 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
654 SMo UNS S32654, Avesta Bulletin 9603

Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
300 Series Stainless Steels Isocorrosion Curves
0-100% H2SO4
?
310M Stainless Steel Type 310M Corrosion Rates in Strong Sulphuric Acid ?
654 SMo
UNS S32654
Isocorrosion Curves
Corrosion Rate = 0.1 mm/y (4 mpy)
0-50% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
Naturally Aerated, Corrosion Rate = 0.1 mm/y (4 mpy)
0-100% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
654 SMo UNS S32654, Avesta Bulletin 9603

Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
904L Isocorrosion Curves
Corrosion Rate = 0.1 mm/y (4 mpy)
0-50% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
Naturally Aerated, Corrosion Rate = 0.1 mm/y (4 mpy)
0-100% H2SO4, 2000 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
0-100% H2SO4, 200 ppm Chloride Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
654 SMo UNS S32654, Avesta Bulletin 9603

Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
Alloy C-22 Corrosion Rate ?
Alloy G-30 Corrosion Rate ?
Carbon Steel Isocorrosion Curves ?
Carpenter 20Cb-3 Corrosion Rate in Non-Aerated H2SO4 at 80°C (176°F)
Corrosion Rate versus Concentration in Boiling H2SO4, 0-50% H2SO4
Isocorrosion Curves 0-100% H2SO4
Corrosion of Annealed 20Cb-3 to Boiling H2SO4 at Various Concentrations (5%, 10% and 25% H2SO4)
20Cb-3 Stainless Steel, Carpenter Technology Brochure
Chlorimet 2 Isocorrosion Curves The Duriron Company, Inc., Bulletin A/3g, April 1987
Chlorimet 3 Isocorrosion Curves The Duriron Company, Inc., Bulletin A/3g, April 1987
Durimet 100 Isocorrosion Curves
Corrosion Rate = 20 mpy
 
Durimet 20 Isocorrosion Curves
Corrosion in Sulphuric Acid
Corrosion Rate = 20 mpy
Durimet 20, Bulletin A/1h, The Duriron Company, Inc., January 1985
Durimet 100, Bulletin A/7g, The Duriron Company, Inc., July 1987
Duriron Isocorrosion Curves Duriron, Duchlor 51, Superchlor, Bulletin A/2g, The Duriron Company, Inc., March 1986
Hastelloy B2 Isocorrosion Curves
Sulphuric Acid
Sulphuric Acid, 200 ppm Chlorides
Hastelloy Alloy B-2, Cabot Stellite Division, Brochure, 1977
Hastelloy C-276 Isocorrosion Curves
Sulphuric Acid
Sulphuric Acid, 2000 ppm Chlorides
Hastelloy Alloy C-276, Haynes International, Bulletin H-2002B
Hastelloy D-205 Corrosion Rates
Reagent Grade Sulphuric Acid at 93°C - Corrosion Rates 20-60% H2SO4
Commercial Grade Sulphuric Acid at 130°C - Corrosion Rates 96-99% H2SO4
Alfa Laval Brochure
?

?
Hastelloy G Corrosion Resistance in Non-Aerated Sulphuric Acid at 80°C (176°F) Carpenter Alloys for Controlling Severe Corrosives, Carpenter Technology Corporation, 9/89-7.5M
Inconel Alloy 686 General Corrosion Resistance
Isocorrosion Curve, 20 mpy (0.51 mm/y)
Isocorrosion Curves
Magazine advertisement
Special Metals Technical Brochure
Lead Isocorrosion Curve
Corrosion Rate = 5 mpy
 
Niobium Isocorrosion Curve
Corrosion Rate = 5 mpy
 
Noridur 9.4460 Isocorrosion Curves
Aerated, Velocity = 10 m/s, Corrosion Rate = 0.5 mm/y
KSB, Klein, Schanzlin & Becker Aktiengesellschaft, I/1980
SAF 2205
UNS S31803
Isocorrosion Curves
Deaerated H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
Corrosion Rate = 0.1 mm/y (4 mpy)
Static Conditions, Corrosion Rate = 0.1 mm/y (4 mpy)
Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
Avesta 2205, UNS 31803, Avesta Bulletin 9060
Sandvik Steel, Bulletin S-1875-ENG, July 1992
SAF 2204
UNS S32304
Isocorrosion Curves
Deaerated H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
0-20% , Static Conditions, Corrosion Rate = 0.1 mm/y (4 mpy)
Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
Avesta SAF 2304, UNS S32304, Avesta Bulletin 9137
Sandvik HT 9067 Isocorrosion Curves
Corrosion Rate = 0.1 mm/y (4 mpy)
Edmeston HT Alloy Brochure
Sandvik SX Corrosion Rates - Static Conditions
Isocorrosion Curves
80-100% , Static Conditions, Corrosion Rate = 0.1 mm/y (4 mpy)
Corrosion Rate = 0.1 mm/y (4 mpy)
Monsanto Enviro-Chem System Brochure
Edmeston Materials System Engineering
Sanicro 28 Isocorrosion Curves
Naturally aerated, Corrosion Rate = 0.1 mm/y (4 mpy)
Stagnant, Corrosion Rate = 0.1 mm/y (4 mpy)
Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
Sandvik Steel, Bulletin S-1875-ENG, July 1992
Titanium Isocorrosion Curves
Deaerated H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
H2SO4 with Copper Sulphate, Corrosion Rate = 0.1 mm/y (4 mpy)
Avesta Sheffield Corrosion Handbook, Avesta Sheffield, 1994
ZeCor Isocorrosion Curve
1 mpy, 90-100% H2SO4
?
Zeron 100 Isocorrosion Curves
Figure 1: Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 2: 0-40% H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 3: 0-60% H2SO4, 2000 mg/L Cl, Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 4: 30-70% H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 5: 70-100% H2SO4, Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 6: 80-100% H2SO4, Ferrous Ions, Corrosion Rate = 0.1 mm/y (4 mpy)
Figure 7: Oleum, 30% SO3, 70-130°C
The Performance of Zeron 100 Super Duplex Stainless Steels in Sulphuric Acid, Weir Materials & Foundries
Zirconium Isocorrosion Curve, Corrosion Rate = 5 mpy Wah Chang Magazine Advertisement

Back to top