Composition and Grade Equivalence
TA9 is a commercially pure titanium grade containing a palladium addition of about 0.2 percent, equivalent to ASTM Grade 7 with UNS designation R52400. The base metal matches the Grade 2 interstitial chemistry, and the palladium is added as the only intentional alloying element.
The small palladium content does not change the mechanical behaviour of the material, so TA9 can be formed, machined and welded exactly like standard Grade 2 titanium while offering far better corrosion resistance in specific media.
Role of the Palladium Addition
Palladium acts as a cathodic alloying element that promotes passivation of the titanium surface. In reducing acids and in crevices where oxygen is depleted, plain titanium loses its protective oxide film and corrodes, while TA9 re-passivates and remains resistant.
The addition is most effective in dilute hydrochloric acid, sulphuric acid, phosphoric acid and hot chloride solutions, where it extends the range of temperature and concentration that the material can tolerate.
Mechanical Properties
TA9 retains the mechanical properties of Grade 2 titanium, with a minimum tensile strength of 345 MPa and a minimum yield strength of 275 MPa in the annealed condition per ASTM B265 and B348. Elongation is typically 20 percent or more.
The material is ductile and easy to weld. Inert gas shielded welding produces joints whose corrosion resistance matches the parent metal, which is essential for chemical plant fabrication.
Corrosion Resistance in Aggressive Media
TA9 resists pitting, crevice attack and stress corrosion cracking in seawater and chloride brines, and it performs reliably in reducing acids where standard titanium grades fail. It is therefore the standard choice for equipment handling hot brine, dilute mineral acids and sour process streams.
The corrosion advantage appears mainly in creviced and low-oxygen conditions. In strongly oxidising media the benefit of palladium is smaller, and standard pure grades perform equally well.
Applications and Supply Forms
TA9 is used for chemical reactor internals, heat exchangers, condensers, brine heaters, anodising equipment, marine components and pharmaceutical plant. It is supplied as plate, sheet, strip, bar, tube, pipe and welding wire, normally in the annealed condition.
Because the palladium content is significant, TA9 is more costly than plain pure titanium, and it is specified where its corrosion performance is proven to justify the premium.
Frequently Asked Questions
Q: What is TA9 titanium?
A: TA9 is a commercially pure titanium grade containing about 0.2 percent palladium, equivalent to ASTM Grade 7 with UNS designation R52400.
Q: Why is palladium added to TA9?
A: Palladium promotes passivation and greatly improves resistance to reducing acids and crevice corrosion.
Q: What is the tensile strength of TA9?
A: TA9 retains Grade 2 properties with a minimum tensile strength of 345 MPa and a minimum yield strength of 275 MPa in the annealed condition.
Q: Where is TA9 used?
A: TA9 is used in chemical reactors, heat exchangers, brine heaters and marine equipment handling hot chloride and reducing media.
Q: Can TA9 be welded?
A: Yes, TA9 welds with inert gas shielding, and the welded joint retains the corrosion resistance of the parent metal.
