Titanium’s reputation as “corrosion-proof” leads many engineers to assume no surface treatment is needed. After machining titanium parts for aerospace and marine applications, we’ve learned when this assumption holds true—and when it can lead to costly failures.
Pure titanium does not corrode like steel, but it can suffer localized corrosion in specific environments. Titanium forms a protective oxide layer that prevents general corrosion in most conditions, but crevice corrosion, pitting, and hydrogen embrittlement can occur in anhydrous environments, concentrated acids, or high-temperature seawater above 200°C.
Discover which environments threaten titanium, how to assess application risk, and when surface treatments offer real protection vs. added cost.
Table of Contents
How long does bare titanium last without treatment?
For most product applications, bare titanium provides 15+ years of service life without surface treatment – longer than typical warranty periods. Industry data from marine and aerospace applications shows unalloyed titanium achieving decades of service in seawater below 160°F. However, parts above 180°F in wet environments or designs with tight crevices may require treatment to avoid premature failure.
Quick Decision Check:
- Operating temperature below 160°F? ✓ Bare titanium likely sufficient
- No tight gaps or stagnant fluid pockets? ✓ Natural oxide protection adequate
- Warranty period under 15 years? ✓ Skip expensive surface treatments
We regularly see projects waste 20-40% of surface finishing budgets on unnecessary anodizing for low-risk applications. Conversely, we’ve consulted on warranty claims where high-temperature seawater exposure (above 180°F) caused crevice corrosion in untreated parts after 3-5 years.
Design Takeaway: Reserve surface treatments for applications exceeding 160°F in wet conditions, designs with crevice-prone geometry, or products requiring 20+ year service life. For standard product applications, bare titanium’s natural protection typically outlasts your warranty requirements while saving significant finishing costs.
Are certain titanium grades more corrosion-resistant than others?
Grade 2 handles 90% of corrosion applications – upgrade only when you have specific aggressive conditions that require it. The performance difference between grades is smaller than most engineers expect, but the cost difference is significant. Use this decision framework instead of defaulting to premium grades.
Grade Selection Decision Tree:
- Hydrochloric acid or reducing acids? → Grade 7 (+$20-30/lb material cost)
- Seawater above 200°F with crevices? → Grade 12 (+$15-25/lb material cost)
- Need high strength + decent corrosion? → Grade 5 (slightly reduced corrosion vs Grade 2)
- Everything else? → Grade 2 (best cost/performance baseline)
We regularly review specs where engineers chose Grade 7 for “better corrosion resistance” in applications where Grade 2 performs identically – wasting thousands in unnecessary material costs. The premium grades solve specific chemistry problems: Grade 7’s palladium addition helps in reducing acids, Grade 12’s molybdenum-nickel improves crevice resistance in hot chlorides.
Design Takeaway: Default to Grade 2 and only upgrade when you can identify the specific aggressive condition requiring premium performance. If you’re unsure about your chemical exposure or operating temperature, specify Grade 2 and consult during design review – the material savings often fund better design solutions.
What design features increase titanium corrosion risk?
Tight crevices and stagnant fluid pockets create the highest corrosion risk in titanium parts – more than material grade or surface finish. Gaps smaller than 0.025″ (0.6mm) where fluids can enter but not circulate freely concentrate corrosive agents and break down titanium’s protective oxide layer. These geometry problems cause more warranty claims than environmental factors.
High-Risk Design Features:
- Overlapping joints and gasket interfaces with trapped moisture
- Deep blind holes or internal cavities without drainage paths
- Thread engagement zones in wet environments
- Sharp internal corners where oxide films thin under stress
From our design reviews, we see expensive field failures when engineers focus on upgrading materials while ignoring basic geometry principles. A well-designed Grade 2 part with proper drainage and generous radii outlasts poorly designed premium alloy components in identical service conditions. The 0.025″ crevice threshold comes from corrosion engineering studies showing where electrolyte stagnation overwhelms titanium’s natural repassivation ability.
Sharp corners concentrate stress and create thin spots in the protective oxide film, particularly problematic under cyclic loading. Adding minimum 0.5mm radii eliminates these stress risers while improving manufacturability.
Design Takeaway: Design out crevices through generous radii and drainage features before considering material upgrades or surface treatments. Simple geometry changes provide better corrosion protection than expensive solutions while reducing manufacturing complexity and part cost.
When does titanium need surface treatment?
Titanium needs surface treatment when operating above 180°F in wet environments or when designs have unavoidable tight crevices. For most applications – indoor equipment, standard marine use below 160°F, automotive parts – bare titanium’s natural protection is sufficient and treatment wastes money.
Treatment Required:
- Temperature above 180°F in seawater/corrosive fluids
- Tight crevices that can’t be designed out
- Anhydrous environments (water-free alcohols, dry chlorine)
- Warranty periods exceeding 20 years in harsh outdoor exposure
Treatment Not Required:
- Indoor/atmospheric conditions at any temperature
- Seawater below 160°F with good drainage
- Standard automotive or consumer product applications
We regularly see 30-50% finishing cost waste on unnecessary treatments for low-risk applications. Conversely, untreated high-temperature marine equipment often fails within 5 years due to crevice corrosion above 180°F.
Design Takeaway: Specify treatment only when you exceed the 180°F threshold in wet conditions or have unavoidable crevice geometry. Most applications operate well below these limits, making treatment an unnecessary expense.
When should you specify anodizing vs passivation for titanium?
Choose anodizing for the aggressive conditions identified above, passivation for cleaning after machining when no treatment is actually needed. If you determined treatment is necessary, anodizing provides the enhanced protection. If bare titanium works but you want surface optimization, passivation handles that at lower cost.
Selection Logic:
- Aggressive conditions requiring treatment (above 180°F, unavoidable crevices)? → Anodizing ($8-15/part)
- Want to clean machining residue on low-risk parts? → Passivation ($2-5/part)
- Need color or specific surface properties? → Anodizing only option
We see engineers specify expensive anodizing for parts operating in mild conditions where passivation provides identical performance – like parts below 160°F in standard environments. Anodizing’s enhanced protection only benefits applications that exceed titanium’s natural limits.
Design Takeaway: If the previous section said no treatment needed, save money and skip both. If treatment is required for aggressive service, choose anodizing. Passivation works when you want surface cleaning without the expense of enhanced protection you don’t actually need.
What's the cheapest titanium corrosion protection?
The cheapest protection is designing out corrosion risks rather than treating the surface – eliminating tight crevices and staying below 180°F saves more money than any surface treatment. When treatment is actually required, passivation at $2-5 per part provides the most cost-effective enhancement of titanium’s natural protection. Anodizing costs 3x more but only adds value in truly aggressive conditions.
Cost-Effective Protection Strategies:
- Design optimization (free): Eliminate crevices, add drainage, use generous radii
- Passivation ($2-5/part): Clean surface, optimize natural oxide layer
- Grade 2 titanium baseline ($8-12/lb): Best corrosion/cost balance for 90% of applications
- Anodizing ($8-15/part): Only when enhanced protection justifies 3x cost premium
We regularly save clients 40-60% on corrosion protection budgets by addressing geometry issues during design review rather than specifying expensive treatments after the fact. A $500 design change often eliminates the need for $2000 worth of surface treatments across a production run. The most expensive approach is discovering corrosion issues after production starts.
Design Takeaway: Invest design time in corrosion-resistant geometry before considering surface treatments. If treatment is genuinely needed based on previous sections, passivation provides the best value for most applications. Reserve anodizing budget for parts that actually operate in the aggressive conditions requiring enhanced protection.
Do surface treatments affect titanium tolerances?
Anodizing adds approximately 0.0003″ to all surfaces, which only matters for tight fits under ±0.001″ – most standard clearances aren’t affected. Passivation doesn’t change dimensions meaningfully. Plan for anodizing thickness during design or specify masking for critical surfaces to avoid costly rework.
When Tolerance Effects Matter:
- Precision fits tighter than ±0.001″ → Design 0.0003″ smaller or mask during treatment
- Standard clearances (±0.005″ or looser) → No design changes needed
- Threaded holes → Mask threads or plan post-treatment tapping
- Bearing surfaces and seals → Mask or machine after treatment
Design Specification Options:
- Design undersized by 0.0003″ if anodizing planned
- Call out “mask critical surfaces” on drawings (adds ~$2-5 per masked feature)
- Specify “machine after anodizing” for precision features (adds ~$10-20 per machined surface)
From our experience, tolerance problems occur when engineers add anodizing late in the design process without adjusting part dimensions. We see costly rework when anodized shafts no longer fit their bearings or anodized housings create interference with assembled components.
Design Takeaway: If your fits are looser than ±0.001″, anodizing thickness won’t cause problems. For precision applications, decide on anodizing early and either design smaller or budget for masking/post-machining. Passivation can be specified without dimensional concerns.
Conclusion
Titanium’s natural corrosion resistance eliminates surface treatments for most applications below 180°F – saving significant finishing costs. Reserve anodizing for truly aggressive conditions and focus design efforts on eliminating crevices rather than expensive surface solutions. Contact us to explore manufacturing solutions tailored to your titanium part requirements.
Frequently Asked Questions
Yes, but post-weld anodizing requires careful surface preparation to remove heat tint and contamination. We recommend anodizing individual components before assembly when possible, as complex geometries and crevices created during welding can trap electrolytes and reduce treatment effectiveness in those areas.
Evaluate three factors: operating temperature above 180°F in wet conditions, unavoidable tight crevices in your design, and warranty requirements exceeding 20 years. If your application doesn’t meet these criteria, bare titanium’s natural oxide protection typically outlasts product lifecycles while avoiding unnecessary finishing costs.
Passivation optimizes titanium’s natural corrosion resistance by removing machining contaminants and ensuring uniform oxide formation, but doesn’t provide enhanced protection like anodizing. It’s cost-effective surface preparation ($2-5 per part) when you want clean surfaces without the expense of treatments you don’t actually need.
We routinely hold ±0.0005″ on critical features by designing parts 0.0003″ undersized before anodizing or masking precision surfaces during treatment. Standard anodizing adds 0.0001-0.0003″ thickness, so planning for this coating buildup during design prevents tolerance issues and costly rework.
Design out crevices through generous radii (minimum 0.5mm), drainage features, and avoiding overlapping joints rather than relying on surface treatments. A $500 design modification often eliminates the need for expensive anodizing across entire production runs, providing better protection at lower total cost.
Grade 2 provides excellent corrosion resistance in seawater below 180°F at the lowest material cost. Grade 7 with palladium addition offers superior performance in reducing acids but costs 3-5x more. For standard marine hardware, Grade 2’s performance typically justifies the significant cost savings over premium alloys.
