Titanium Grades Compared: Strength, Corrosion Resistance & Cost Breakdown (GR1, GR2, GR3, GR4, GR7)

2025-06-04

Titanium is a highly sought-after material in industries such as aerospace, chemical processing, medical, and marine due to its exceptional strength-to-weight ratio, corrosion resistance, and biocompatibility. Among the various grades defined by ASTM B348, Grades 1 through 4 represent commercially pure titanium (CP-Ti), while Grade 7 is a palladium-enhanced alloy designed for extreme corrosion resistance.

This article provides a detailed, multi-dimensional comparison of GR1, GR2, GR3, GR4, and GR7, covering composition, mechanical and physical properties, corrosion behavior, processability, pricing, and applications.

1. Material Type & Composition Overview

Grade	Type	Key Composition (Balance: Ti)	Notable Characteristics
GR1	CP-Ti (Softest)	99.5% Ti, ≤0.18% O₂	Highest ductility, excellent formability
GR2	CP-Ti (Standard)	99.2% Ti, ≤0.25% O₂	Balanced strength & corrosion resistance
GR3	CP-Ti (Medium Strength)	99.1% Ti, ≤0.35% O₂	Higher strength than GR1/GR2
GR4	CP-Ti (Strongest CP)	98.9% Ti, ≤0.40% O₂	Highest strength among CP grades
GR7	Ti-0.15% Pd Alloy	99.1% Ti, 0.12-0.25% Pd	Superior corrosion resistance

GR1 to GR4 are unalloyed titanium, with increasing oxygen content enhancing strength but reducing ductility.
GR7 contains palladium (Pd), which drastically improves corrosion resistance in aggressive environments.

2. Mechanical & Physical Properties (Annealed Condition)

Property	GR1	GR2	GR3	GR4	GR7
Tensile Strength (MPa)	240-370	345-480	450-600	550-750	345-480
Yield Strength (MPa)	170-310	275-410	380-520	485-620	275-410
Elongation (%)	24+	20+	18+	15+	20+
Hardness (HV)	100-150	150-200	200-250	250-300	150-200
Density (g/cm³)	4.51	4.51	4.51	4.51	4.51

GR1 is the softest and most ductile, ideal for deep drawing.
GR4 is the strongest among CP grades but less formable.
GR7 has similar mechanical properties to GR2 but with enhanced corrosion resistance.

3. Corrosion Resistance Profile

Environment	GR1	GR2	GR3	GR4	GR7
Seawater	Good	Good	Good	Good	Excellent
Chloride Solutions	Moderate	Moderate	Moderate	Moderate	Exceptional
Oxidizing Acids (HNO₃)	Good	Good	Good	Good	Excellent
Reducing Acids (HCl, H₂SO₄)	Poor	Poor	Poor	Poor	Excellent
Alkaline Solutions	Good	Good	Good	Good	Excellent

GR7 outperforms all other CP-Ti grades due to palladium’s catalytic effect, preventing corrosion in reducing acids and chloride-heavy environments.
GR1-GR4 perform well in oxidizing conditions but struggle in reducing acids.

4. Processing & Weldability

Grade	Formability	Weldability	Machinability
GR1	Excellent (Best for deep drawing)	Excellent	Good
GR2	Very Good	Excellent	Good
GR3	Good	Good	Moderate
GR4	Fair (Prone to cracking)	Good	Moderate
GR7	Very Good	Excellent	Good

GR1 & GR2 are preferred for sheet metal and welding applications.
GR4 is harder to form but offers higher strength.
GR7 welds similarly to GR2 but requires care to avoid contamination.

5. Price & Supply Overview

Grade	Relative Cost	Market Availability
GR1	Low-Medium	Widely Available
GR2	Medium	Most Common Grade
GR3	Medium-High	Limited Use
GR4	High	Specialty Applications
GR7	Very High (Due to Pd)	Limited, High-Performance Use

GR2 is the most economical and widely used.
GR7 is significantly more expensive due to palladium content (~10x cost of GR2).

6. Recommended Applications

Grade	Typical Uses
GR1	Chemical processing linings, heat exchangers, marine components, medical implants (where ductility is key).
GR2	Aerospace structures, desalination plants, heat exchangers, surgical instruments.
GR3	Pressure vessels, hydraulic systems, airframe components.
GR4	High-strength fasteners, cryogenic vessels, orthopedic implants.
GR7	Chemical processing (HCl, H₂SO₄), offshore oil & gas, pharmaceutical reactors, extreme marine environments.