Titanium Alloy Casting Pickling Technology
1. Raw Materials and Equipment
Pickling Solution Raw Materials
Refer to Table 1.
Equipment
Pickling Tank: Made of stainless steel, lined with rigid polyvinyl chloride (PVC) plastic panels, or entirely made of rigid PVC plastic.
Temperature Control & Ventilation: The pickling tank is equipped with a cooling system, temperature display, anti-evaporation cover, and exhaust ventilation system.
Fixtures & Drying: Fixtures and clamps are made of titanium alloy or protective-coated stainless steel. Drying equipment operates at a maximum temperature of 105°C.
2. Process Flow
Sandblasting to Remove Oxide Scale → Organic Solvent Cleaning → Cold Water Rinse → Pickling → Cold Water Rinse → Flowing Cold Water Rinse → Spray Rinse → Drying → Quality Inspection
Oil Contamination Cleaning: Gasoline, ethanol, or acetone.
Fingerprint Removal After Pickling: Clean with a 1:1 acetone and butanol mixture, then wipe with industrial ethanol.
3. Pickling Solution
Solution 1 is generally used for titanium alloy castings, while Solution 2 is used for corrosion-resistant titanium alloys.
Refer to Table 2.
4. Pickling Operation
Operation Method: Castings should be moved up and down or swung to ensure sufficient contact with the acid solution.
Temperature Control: Monitor pickling solution temperature to prevent overheating.
Time Control: The pickling time is determined by the material reduction rate. Initially, measure thickness or calculate mass loss after 1–5 minutes.
Water Rinsing Requirements:
Cold water below room temperature or warm water (30–60°C).
Cleaning water resistivity ≥1200Ω·cm (25°C), TDS ≤600mg/L, pH 5.5–8.5.
Drying: Use oil-free compressed air or an oven.
5. Pickling Solution Management
The solution is prepared by adding chemicals in proportion and stirring evenly. The liquid depth should not exceed two-thirds of the tank depth.
Titanium ion concentration should be analyzed every four weeks. If it exceeds 25 g/L and the pickling rate is insufficient, the solution should be discarded.
Waste liquid should be sealed and processed by a qualified professional organization.
6. Acid Gas Purification
Acid gases generated during pickling must be purified before discharge to meet environmental standards.
7. Quality Control
Appearance Inspection
The surface should be smooth with a metallic luster or appear silver-white or gray-white.
No pitting, unremoved stains, oil contamination, fingerprints, or mechanical damage.
Hydrogen Content Control
Maintain solution composition and temperature control to avoid hydrogen absorption.
Hydrogen content measurement follows GB/T 4698.15.
If hydrogen content exceeds 0.003%, investigate the cause and conduct vacuum annealing (refer to Table 3).
Alpha Layer Control
The alpha layer on the casting surface should be completely removed after pickling.
Inspection methods include metallographic or microhardness testing. If residual layers are found, re-pickling is required.
Final Inspection
Uniform surface roughness without oxide layers, oil, fingerprints, or other contaminants.
Pure water test: No water film rupture after immersion.
Sandblasting should not cause deformation, and blasting materials must be regularly inspected.
This process strictly adheres to national standards to ensure pickling quality and environmental safety.
