Titanium Corrosion and Titanium Alloy Corrosion Data from Titanium Processing Center

The need for titanium corrision and titanium allow corrosion data

Titanium alloys were originally developed in the early 1950s for aerospace applications, in which their high strength-to-density ratios were especially attractive. Although titanium alloys are still vital to the aerospace industry for these properties, recognition of the excellent resistance of titanium to many highly corrosive environments, particularly oxidizing and chloride-containing process streams, has led to widespread non-aerospace (industrial) applications.

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Reagent	Conc. (%)	Temp.°C	Time of Exposure (Hrs.)	Corrosion Rate For Titanium (ipy)
Acetic Acid - Glacial	99	B.P. (199)	300	<.0001
Acetic Acid plus traces of Mn,Ba,Co	70	50-90	1044	<.0001
Acetic Acid plus 25% Adipic, 3% Formic	65	122	2664	.0001
Adiponitrile Soln. containing NH3,H2O	Vapor	350-380	1649	.0000-.0003
Adipyl Chloride & Chlorobenzene Soln.	-	-	-	<.0001
Adipic Acid Soln. plus 15-20% Glutaric, 2% Acetic Acid	25	195-200	1077	.0000
Acetic Anhydride	99	20	300	.0001
Aqua Regia (3 HCI-1 HNO3 or 1 HCI-3 HNO3)	-	Room	-	.005
Aluminum Chloride	25	60	144	nil
Aluminum Chloride	25	100	144	.258
Ammonia (20%) + Sodium Hydoxide(2%) + Water	-	-	2250	.00024
Ammonium Chloride	sat.	100	144	nil
Ammonium Hydroxide	28	Room	300	<.0001
Aniline (98%) + Aluminum Chloride (2%)	-	316	24	.840
Aniline Hydrochloride	20	100	-	nil
Barium Chloride	20	100	144	.00001
Benzene + traces of HCI, NaCI salts, CS2	Vapor & Liq.	80	2268	.0002
Benzene + traces of HCI, NaCI salts, CS2	Liquid	40 - 50	2650	.001
Bromine	Liquid	30	3 min.	Rapid Attack
Bromine	Vapor	30	24	<.0001
Citric Acid	50	100	144	.00005
Cyclohexane + traces of Formic Acid	-	150	2820	.0001
Calcium Chloride	28	Boil.	300	<.0001
Calcium Hypochlorite	6	35	-	<.005
Carbon Tetrachloride + 1% Water	Boiling	300	-	<.0001
Chloroacetic Acid	30	80	-	.0008
Chloroacetic Acid	100	Boil.	-	<.0005
Chlorine Gas(Water Saturated)	100	75	30	<.0001
Chlorine Gas(Dry Commercial)(<.1%H2O)	100	30	-	Rapid Attack Ignited & Burned
Chromic Acid	10	Boil.	300	<.0001
Cupric Chloride	40	Boil.	300	<.0001
Cupric Chloride	40	Boil.	300	<.0001
Cuprous Chloride	50	90	3360	<.0001
Chrome Alum	-	-	-	<.0001
Dichloro Acetic Acid	100	100	144	<.0005
Ethyl Alcohol	95	Boil.	-	<.0005
Formaldehyde(50%) + H2SO4(2.5%)	-	70	144	<.0001
Formamide Vapor in pres. of Mn Catalyst	-	300	-	.012
Formic Acid(H2O Soln.) + Traces of Cychlohexane	9	40-50	2117	<.0001
Ferric Chloride	10	Boil.	300	<.0001
Formaldehyde	37	Boil.	300	<.0001
Formic Acid	50	Room	300	.0001-.200 Borderline Passivity
Formic Acid(Aerated)	90	100	144	.00005
Formic Acid(Nonaerated & Static)	25	100	144	.096
Gas Mixture-H2, CO, & CO2	-	300	1270	No Attack Gained Weight
Hydrogen Peroxide (C.P.)	30	Room	-	<.012
Hydrogen Peroxide (A.C.S)	30	Room	-	<.0005
Hydroxyacetic Acid	-	40	1500	.0012
Hydrogen Sulfide Saturated Water	-	Room	300	<.0001
Hydrochloric Acid (Aerated)	.05	35	144	.00004
Hydrochloric Acid (Aerated)	1	60	144	.00011
Hydrochloric Acid (Aerated)	1	100	144	.0185
Hydrochloric Acid (Aerated)	2	100	144	.272
Hydrochloric Acid (Aerated)	3	60	144	.00038
Hydrochloric Acid (Aerated)	3	100	144	.696
Hydrochloric Acid (Aerated)	4	60	144	.043
Hydrochloric Acid (Aerated)	5	Room	144	<.0001
Hydrochloric Acid (Aerated)	5	60	144	.042
Hydrochloric Acid (Aerated)	7.5	35	144	.015
Hydrochloric Acid (Aerated)	10	35	144	.042
Hydrochloric Acid (Aerated)	15	35	144	.0647
Hydrochloric Acid (Aerated)	20	Room	144	.0204
Hydrochloric Acid (Aerated)	37	35	144	.600
Hydrochloric Acid(10%) + CuSo4(.05%)	-	66	-	.00132
Hydrochloric Acid(10%) + CuSo4(.10%)	-	66	-	.000684
Hydrochloric Acid(10%) + CuSo4(.20%)	-	66	-	nil
Hydrochloric Acid(10%) + Nitric Acid(.70%)	-	66	-	.00132
Hydrochloric Acid (Unaerated)	1	35	144	.00013
Hydrochloric Acid (Unaerated)	1	Boil.	300	.0001-.080 Borderline Passivity
Hydrochloric Acid (Unaerated)	3	Boil.	300	24
Hydrochloric Acid (Unaerated)	5	50	48	.077
Hydrochloric Acid (Unaerated)	5	Boil.	300	.600
Hydrochloric Acid (Unaerated)	10	Room	300	.0001-.020 Borderline Passivity
Hydrofluoric Acid	1	Room	300	2.50
Hydrofluoric Acid(Anhydrous)	100	Room	300	.024
Lactic Acid	85	Boil.	-	.0002
Lactic Acid	100	Boil.	48	.00023-.00030
Magnesium Chloride	20	100	144	.00039
Maganous Chloride	20	100	144	nil
Mercuric Chloride	sat.	100	144	.00004
Nickel Chloride	20	100	144	.00011
Nitric Acid(Aerated)	5	35	144	.00008
Nitric Acid(Aerated)	5	100	144	.00061
Nitric Acid(Aerated)	10	35	144	.00016
Nitric Acid(Aerated)	10	100	144	.00029
Nitric Acid(Aerated)	20	35	144	.00018
Nitric Acid(Aerated)	20	290	48	.012
Nitric Acid(Aerated)	30	100	144	.00027
Nitric Acid(Aerated)	40	100	144	.00023
Nitric Acid(Aerated)	40	200	48	.024
Nitric Acid(Aerated)	50	100	144	.00023
Nitric Acid(Aerated)	60	100	144	.00028
Nitric Acid(Aerated)	65	175	48	.0024
Nitric Acid(Aerated)	69.5	100	144	.00074
Nitric Acid(Aerated)	70	270	48	.048
Nitric Acid(Aerated)	65	Boil.(121)	240	.00276
Nitric Acid(Aerated)	98	Room	-	<.0001
Nitric Acid(Aerated)	Red Fuming	Room	336	.00007 (consult reference)
Nitric Acid(Aerated)	Fuming	50	-	.00005
Nitric Acid(Aerated)	Fuming	70	-	.0001
Nitric Acid(Aerated)	White Fuming	Room	-	.0001
Nitric Acid(Aerated)	Fuming	122	-	.00005
Nitric Acid(Aerated)	Fuming	160	-	.00006
Nitric Paranitrtoluene	20-25	180	240	.00024
Nitric-Hydrofluoric(15HNO3-HF)	-	Room	-	Not Recommended
Nitric-Adiptic Mixtures (38% HNO3-17%Adiptic)	-	90-95	169	.000-.0006
Oxalic Acid	1	37	144	>.012
Phosphoric Acid	10	80	300	.072
Phosphoric Acid	85	Room	300	.0084
Phosphoric Acid	Vapor	190	1600	Sample Dissolved
Photographic Emulsions	-	-	-	<.0001
Sea Water(Kure Beach)	-	Ambient	120	<.0001
Sodium Chloride	Saturated	Boil.	300	<.0001
Sodium Hydroxide	10	Boil.	300	.00084
Sodium Hydroxide	28	Room	300	<.0001
Sodium Hydroxide	40	80	300	.005
Sodium Hypochlorite	5-6CI2	Room	300	<.0001
Sodium Sulfide	10	Boiling	300	.001
Silver Bromide(suspended in gel)	-	-	-	<.0001
Silver Bromide+2% Silver Iodide	-	-	-	<.0001
Stannic Chloride	24	60	144	.00016
Stearic Acid	100	180	300	<.0001
Sulfur (Molten)	100	240	300	<.0001
Sulfur Plus Water	-	Room	300	<.0001
Sulfur Dioxide(Water Saturated)	-	Room	300	<.0001
Sulfuric Acid	1	Room	300	<.0001
Sulfuric Acid	1	Boil.	300	.360
Sulfuric Acid	3	35	144	.00018
Sulfuric Acid	5	Room	300	.0001-.009 Borderline Passivity
Sulfuric Acid	5	Boil.	300	.960
Sulfuric Acid	10	Room	300	.0072
Sulfuric Acid	10	50	48	.073
Sulfuric Acid	40	Room	300	.060
Sulfuric Acid	65	Room	300	.072
Sulfuric Acid	78	Room	300	.600
Sulfuric Acid	95	Room	300	.960
Sulfuric Acid	104	Room	300	.240
Sulfuric Acid (Aerated)	10	35	144	.050
Sulfuric Acid (Aerated)	25	35	144	.131
Sulfuric Acid (Aerated)	40	35	144	.341
Sulfuric Acid (Aerated)	50	35	144	.156
Sulfuric Acid (Aerated)	65	35	144	.026
Sulfuric Acid (Aerated)	75	35	144	.0419
Sulfuric Acid (Aerated)	96.5	35	144	.222
Sulfuric Acid + H2S, FeS. & Ti Sulphate	-	-	-	.00001
Sulfuric Acid + MnO2(.5%)	40	Room	300	.0001 - .06 Borderline Passivity
Sulfuric Acid + Nitric(.70%)	-	38	300	.00132
Sulfuric Acid + Nitric(.48%)	-	Room	300	.001
Sulfuric Acid + Nitric(.83%) + H2O	-	Room	300	.0008
Sulfuric Acid + CuSO4(.05-1.00%)	-	38	-	.00132
Sulfurous Acid	6	Room	30	.000028
Solution of Wet Cl2, Cl2 Water, & HCl	-	5-25	576	.0000131
Tannic Acid	25	100	144	nil
Tannic Acid	50	100	144	.00002
Trichloroethylene (Stabilized) + 1% h2O	100	Boil.	300	<.0001
Trichloroethylene (Unstabilized) + 1% h2O	100	Boil.	300	<.0001
Zinc Chloride	20	100	144	<.0001
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Corrosion of Titanium and Titanium Alloys

Following content courtesy of Key to Metals:
The World's Most Comprehensive NONFERROUS Metals Database

Titanium alloys were originally developed in the early 1950s for aerospace applications, in which their high strength-to-density ratios were especially attractive. Although titanium alloys are still vital to the aerospace industry for these properties, recognition of the excellent resistance of titanium to many highly corrosive environments, particularly oxidizing and chloride-containing process streams, has led to widespread non-aerospace (industrial) applications.

Because of decreasing cost and the increasing availability of titanium alloy products, many titanium alloys have become standard engineering materials for a host of common industrial applications. In fact, a growing trend involves the use of high-strength aerospace-founded titanium alloys for industrial service in which the combination of strength to density and corrosion resistance properties is critical and desirable.

The excellent corrosion resistance of titanium alloys results from the formation of very stable, continuous, highly adherent, and protective oxide films on metal surfaces. Because titanium metal is highly reactive and has an extremely high affinity for oxygen, these beneficial surface oxide films form spontaneously and instantly when fresh metal surfaces are exposed to air and/or moisture. In fact, a damaged oxide film can generally reheal itself instantaneously if at least traces of oxygen or water are present in the environment. However, anhydrous conditions in the absence of a source of oxygen may result in titanium corrosion, because the protective film may not be regenerated if damaged.

The nature, composition, and thickness of the protective surface oxides that form on titanium alloys depend on environmental conditions. In most aqueous environments, the oxide is typically TiO2, but may consist of mixtures of other titanium oxides, including TiO2, Ti2O3, and TiO. High-temperature oxidation tends to promote the formation of the chemically resistant, highly crystalline form of TiO, known as rutile, whereas lower temperatures often generate the more amorphous form of TiO, anatase, or a mixture of rutile and anatase.

Although these naturally formed films are typically less than 10 nm thick and are invisible to the eye, the TiO; oxide is highly chemically resistant and is attacked by very few substances, including hot, concentrated HCl, H2SO4, NaOH, and (most notably) HF. This thin surface oxide is also a highly effective barrier to hydrogen.

The methods of expanding the corrosion resistance of titanium into reducing environments include:

• Increasing the surface oxide film thickness by anodizing or thermal oxidation
• Anodically polarizing the alloy (anodic protection) by impressed anodic current or galvanic coupling with a more noble metal in order to maintain the surface oxide film
• Applying precious metal (or certain metal oxides) surface coatings
• Alloying titanium with certain elements
• Adding oxidizing species (inhibitors) to the reducing environment to permit oxide film stabilization

Titanium alloys, like other metals, are subject to corrosion in certain environments. The primary forms of corrosion that have been observed on these alloys include general corrosion, crevice corrosion, anodic pitting, hydrogen damage, and SCC.

In any contemplated application of titanium, its susceptibility to degradation by any of these forms of corrosion should be considered. In order to understand the advantages and limitations of titanium alloys, each of these forms of corrosion will be explained. Although they are not common limitations to titanium alloy performance, galvanic corrosion, corrosion fatigue, and erosion-corrosion are included in the interest of completeness.

General Corrosion

General corrosion is characterized by a relatively uniform attack over the exposed surface of the metal. At times, general corrosion in aqueous media may take the form of mottled, severely roughened metal surfaces that resemble localized attack. This often results from variations in the corrosion rates of localized surface patches due to localized masking of metal surfaces by process scales, corrosion products, or gas bubbles; such localized masking can prevent true uniform surface attack.

Titanium alloys may be subject to localized attack in tight crevices exposed to hot (>70 oC) chloride, bromide, iodide, fluoride, or sulfate-containing solutions. Crevices can stem from adhering process stream deposits or scales, metal-to-metal joints (for example, poor weld joint design or tube-to-tubesheet joints), and gasket-to-metal flange and other seal joints.

Pitting

Pitting is defined as localized corrosion attack occurring on openly exposed metal surfaces in the absence of any apparent crevices. This pitting occurs when the potential of the metal exceeds the anodic breakdown potential of the metal oxide film in a given environment. When the anodic breakdown potential of the metal is equal to or less than the corrosion potential under a given set of conditions, spontaneous pitting can be expected.

Titanium alloys are widely used in hydrogen containing environments and under conditions in which galvanic couples or cathodic charging causes hydrogen to be evolved on metal surfaces. Although excellent performance is revealed for these alloys in most cases, hydrogen embrittlement has been observed.

The surface oxide film of titanium is a highly effective barrier to hydrogen penetration. Traces of moisture or oxygen in hydrogen-containing environments very effectively maintain this protective film, thus avoiding or limiting hydrogen uptake. On the other hand, anhydrous hydrogen gas atmospheres may lead to absorption, particularly as temperatures and pressures increase.

Stress-corrosion cracking (SCC)

Stress-corrosion cracking (SCC) is a fracture, or cracking, phenomenon caused by the combined action of tensile stress, a susceptible alloy, and a corrosive environment. The metal normally shows no evidence of general corrosion attack, although slight localized attack in the form of pitting may be visible. Usually, only specific combinations of metallurgical and environmental conditions cause SCC. This is important because it is often possible to eliminate or reduce SCC sensitivity by modifying either the metallurgical characteristics of the metal or the makeup of the environment.

Another important characteristic of SCC is the requirement that tensile stress is present. These stresses may be provided by cold work, residual stresses from fabrication, or externally applied loads.

The key to understanding SCC of titanium alloys is the observation that no apparent corrosion, either uniform or localized, usually precedes the cracking process. As a result, it can sometimes be difficult to initiate cracking in laboratory tests by using conventional test techniques.

It is also important to distinguish between the two classes of titanium alloys. The first class, which includes ASTM grades 1, 2, 7, 11 and 12, is immune to SCC except in a few specific environments. These specific environments include anhydrous methanol/halide solutions, nitrogen tetroxide (N2O4), and liquid or solid cadmium. The second class of titanium alloys, including the aerospace titanium alloys, has been found to be susceptible to several additional environments, most notably aqueous chloride solutions.

The coupling of titanium with dissimilar metals usually does not accelerate the corrosion of titanium. The exception is in strongly reducing environments in which titanium is severely corroding and not readily passivated. In this uncommon situation, accelerated corrosion may occur when titanium is coupled to more noble metals. In its normal passive condition, materials that exhibit more noble corrosion potentials beneficially influence titanium.

The general corrosion resistance of titanium can be improved or expanded by one or a combination of the following strategies:

• Alloying
• Inhibitor additions to the environment
• Precious metal surface treatments
• Thermal oxidation
• Anodic protection.

Alloying

Perhaps the most effective and preferred means of extending resistance to general corrosion in reducing environments has been by alloying titanium with certain elements. Beneficial alloying elements include precious metals (>0.05 wt% Pd), nickel ( >= 0.5 wt%), and/or molybdenum (>= 4 wt%). These additions facilitate cathodic depolarization by providing sites of low hydrogen overvoltage, which shifts alloy potential in the noble direction where oxide film passivation is possible. Relatively small concentrations of certain precious metals (of the order of 0.1 wt%) are sufficient to expand significantly the corrosion resistance of titanium in reducing acid media.

These beneficial alloying additions have been incorporated into several commercially available titanium alloys, including the titanium-palladium alloys (grades 7 and 11), Ti-0.3Mo-0.8Ni (grade 12), Ti-3Al-8V-6Cr-4Zr-4Mo, Ti-15Mo-5Zr, and Ti-6Al-2Sn-4Zr-6Mo. These alloys all offer expanded application into hotter and/or stronger HCl, H2SO4, H3PO4, and other reducing acids as compared to unalloyed titanium. The high-molybdenum alloys offer a unique combination of high strength, low density, and superior corrosion resistance. Fig 1. Corrosion of dissimilar metals coupled to titanium in flowing ambient-temperature seawater.

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