corrosion resistance of titanium Titanium Metals Corporation TIMET® The world’s complete titanium resource Alloys products expertise Titanium Metals Corporation service inventory TIMET 40 YEAR WARRANTY In most power plant surface condenser tubing, tubesheet and service water pipe applications, TIMET CODEWELD® Tubing and CODEROLL® Sheet, Strip and Plate can be covered by written warranties against failure by corrosion for a period of 40 years. For additional information and copies of these warranties, please contact any of the TIMET locations shown on the back cover of this brochure. The data and other information contained herein are derived from a variety of sources which TIMET believes are reliable. Because it is not possible to anticipate specific uses and operating conditions, TIMET urges you to consult with our technical service personnel on your particular applications. A copy of TIMET’s warranty is available on request. TIMET ®, TIMETAL®, CODEROLL® and CODEWELD® are registered trademarks of Titanium Metals Corporation. FORWARD Since titanium metal first became a This brochure summarizes the commercial reality in 1950, corrosion corrosion resistance data accumulated resistance has been an important in over forty years of laboratory consideration in its selection as an testing and application experience. engineering structural material. The corrosion data were obtained Titanium has gained acceptance using generally acceptable testing in many media where its corrosion methods; however, since service resistance and engineering properties conditions may be dissimilar, TIMET have provided the corrosion and recommends testing under the actual design engineer with a reliable and anticipated operating conditions. economic material. i CONTENTS Forward ........................................................................... i Introduction ...................................................................... 1 Chlorine, Chlorine Chemicals, and Chlorides ............................ 2 Chlorine Gas Chlorine Chemicals Chlorides Bromine, Iodine, and Fluorine ............................................... 4 Resistance to Waters ........................................................... 5 Fresh Water – Steam Seawater General Corrosion Erosion Stress Corrosion Cracking Corrosion Fatigue Biofouling/MIC Crevice Corrosion Galvanic Corrosion Acids............................................................................... 8 Oxidizing Acids Nitric Acid Red Fuming Nitric Acid Chromic Acid Reducing Acids Hydrochloric Acid Sulfuric Acid Phosphoric Acid Hydrofluoric Acid Sulfurous Acid Other Inorganic Acids Mixed Acids Alkaline Media ...................................................................17 Inorganic Salt Solutions .......................................................17 Organic Chemicals ..............................................................18 Organic Acids ....................................................................19 Oxygen.............................................................................20 Hydrogen ..........................................................................21 Sulfur Dioxide and Hydrogen Sulfide .......................................22 Nitrogen and Ammonia .........................................................23 Liquid Metals ....................................................................23 Anodizing and Oxidation Treatments .......................................24 Types of Corrosion ..............................................................25 General Corrosion Crevice Corrosion Stress Corrosion Cracking Anodic Breakdown Pitting Hydrogen Embrittlement Galvanic Corrosion References ........................................................................31 Appendix ..........................................................................33 INTRODUCTION Many titanium alloys have been Titanium offers outstanding resistance Titanium and its alloys provide excellent developed for aerospace applications to a wide variety of environments. resistance to general localized attack where mechanical properties are the In general, TIMETAL Code 12 and under most oxidizing, neutral and primary consideration. In industrial TIMETAL 50A .15Pd extend the inhibited reducing conditions. They also applications, however, corrosion usefulness of unalloyed titanium to remain passive under mildly reducing resistance is the most important property. more severe conditions. TIMETAL 6-4, conditions, although they may be The commercially pure (c.p.) and alloy on the other hand, has somewhat less attacked by strongly reducing or grades typically used in industrial service resistance than unalloyed titanium, but complexing media. are listed in Table 1. Discussion of is still outstanding in many environments Titanium metal’s corrosion resistance is corrosion resistance in this brochure will compared to other structural metals. due to a stable, protective, strongly be limited to these alloys. Recently, ASTM incorporated a series of adherent oxide film. This film forms In the following sections, the resistance new titanium grades containing 0.05% instantly when a fresh surface is of titanium to specific environments is Pd. (See Table 1 below.) These new exposed to air or moisture. According to (1) discussed followed by an explanation of grades exhibit nearly identical corrosion Andreeva the oxide film formed on the types of corrosion that can affect resistance to the old 0.15% Pd grades, titanium at room temperature titanium. The principles outlined and the yet offer considerable cost savings. TIMET immediately after a clean surface is data given should be used with caution is pleased to offer these new titanium exposed to air is 12-16 Angstroms thick. as a guide for the application of titanium. grades: 16 (TIMETAL 50A .05Pd), After 70 days it is about 50 Angstroms. In many cases, data were obtained in the 17 (TIMETAL 35A .05Pd), and It continues to grow slowly reaching a laboratory. Actual in-plant environments 18 (TIMETAL 3-2.5 .05Pd). thickness of 80-90 Angstroms in 545 often contain impurities which can exert Throughout this brochure, wherever days and 250 Angstroms in four years. their own effects. Heat transfer information is given regarding Grade 7 The film growth is accelerated under conditions or unanticipated deposited (TIMETAL 50A .15Pd), these new strongly oxidizing conditions, such as residues can also alter results. Such grades may be substituted. As always, heating in air, anodic polarization in an factors may require in-plant corrosion this information should only be used as electrolyte or exposure to oxidizing tests. Corrosion coupons are available a guideline. TIMET technical agents such as HNO3, CrO3 etc. from TIMET for laboratory or in-plant representatives should be consulted to The composition of this film varies from assure proper titanium material testing programs. A tabulation of TiO2 at the surface to Ti2O3, to TiO at available general corrosion data is given selection. Additional information the metal interface.(2) Oxidizing in the Appendix. concerning these new grades may be conditions promote the formation of obtained from TIMET. TiO2 so that in such environments the film is primarily TiO2. This film is transparent in its normal thin configuration and not detectable by visual means. Table 1 A study of the corrosion resistance of Titanium alloys commonly used in industry titanium is basically a study of the properties of the oxide film. The oxide TIMET film on titanium is very stable and is Designation ASTM UNS Ultimate Tensile Yield Strength (min.) Nominal only attacked by a few substances, most TIMETAL Grade Designation Strength (min.) 0.2% Offset Composition notably, hydrofluoric acid. Titanium is 35A 1 R50250 35,000 psi 25,000 psi C.P. Titanium* capable of healing this film almost 50A 2 R50400 50,000 psi 40,000 psi C.P. Titanium* instantly in any environment where a 65A 3 R50550 65,000 psi 55,000 psi C.P. Titanium* trace of moisture or oxygen is present 75A 4 R50700 80,000 psi 70,000 psi C.P. Titanium* 6-4 5 R56400 130,000 psi 120,000 psi 6% AI, 4% V because of its strong affinity for oxygen. 50A .15Pd 7 R52400 50,000 psi 40,000 psi Grade 2+0.15% Pd Anhydrous conditions in the absence of 3-2.5 9 R56320 90,000 psi 70,000 psi 3.0% AI, 2.5% V a source of oxygen should be avoided 35A .15Pd 11 R52250 35,000 psi 25,000 psi Grade 1+0.15% Pd since the protective film may not be Code 12 12 R53400 70,000 psi 50,000 psi 0.3% Mo, 0.8% Ni regenerated if damaged. 50A .05Pd 16 R52402 50,000 psi 40,000 psi Grade 2+0.05% Pd 35A .05Pd 17 R52252 35,000 psi 25,000 psi Grade 1+0.05% Pd 3-2.5 .05Pd 18 R56322 90,000 psi 70,000 psi Grade 9+0.05% Pd *Commercially Pure (Unalloyed) Titanium 1 CHLORINE, CHLORINE CHEMICALS AND CHLORIDES Chlorine and chlorine compounds in mechanical damage to titanium in Chlorides aqueous solution are not corrosive chlorine gas under static conditions at Titanium has excellent resistance to toward titanium because of their room temperature (Figure 1).(4) Factors corrosion by neutral chloride solutions strongly oxidizing natures. Titanium is such as gas pressure, gas flow, and even at relatively high temperatures unique among metals in handling temperature as well as mechanical (Table 3). Titanium generally exhibits these environments. damage to the oxide film on the very low corrosion rates in chloride titanium, influence the actual amount of The corrosion resistance of titanium environments. to moist chlorine gas and chloride- moisture required. Approximately