ASTM B600- Guide for Descaling and Cleaning Titanium and Titanium Alloy Surfaces

Standard Guide for Descaling and Cleaning Titanium and Titanium Alloy Surfaces

ASTM B600 provides recommended procedures for cleaning, descaling, and preparing the surfaces of titanium and titanium alloys before:

Inspection

Welding

Fabrication

Plating or coating

Assembly for critical service (e.g., aerospace, chemical processing)

This guide is not a specification—it offers general best practices rather than strict requirements.

Why Surface Preparation is Important

Removes oxide scale, contaminants, and embedded foreign material

Enhances weld quality, bonding, and corrosion resistance

Essential before electroplating, painting, or chemical exposure

Recommended Surface Treatments

ASTM B600 outlines several methods for surface cleaning, including:

1. Mechanical Cleaning

Grit blasting (with approved media like aluminum oxide or glass beads)

Brushing (stainless steel or titanium brushes)

Machining or grinding (with titanium-compatible tools)

Avoid:

Iron-based abrasives (can cause galvanic contamination)

Cross-contamination from carbon steel tools

2.Chemical Descaling / Pickling

Used to remove oxide scale and contaminated surface layers:

Typical Pickling Solution:

Nitric acid (HNO₃) + Hydrofluoric acid (HF)

e.g., 20–40% HNO₃ + 2–8% HF

Immersion time: 1–15 minutes (depending on scale thickness)

Removes:

Alpha case

Weld heat tint

Mill scale

Oxides

Safety caution: HF is hazardous-requires PPE, proper ventilation, and neutralization systems.

3. Degreasing and Cleaning

Before any acid or welding operation, remove oils and organic contaminants:

Alkaline cleaning (e.g., sodium metasilicate-based solutions)

Solvent degreasing (e.g., acetone, alcohol, or commercial cleaners)

Ultrasonic cleaning for small/complex parts

Final rinse: with deionized or distilled water to avoid mineral spotting.

4. Passivation (Optional)

Some critical components may undergo passivation to further:

Remove minor contaminants

Enhance corrosion resistance

Method: soak in nitric acid solution (20–30%) without HF.

Inspection After Cleaning

After surface prep:

Visually inspect under good lighting

Surfaces should be uniform, free of scale, free of stains or debris

No discoloration, oil films, or visible embedded materials

Advanced: optional fluorescent penetrant inspection (FPI) or white light inspection for surface flaws.

Practices to Avoid

Steel wool or carbon steel tools: Iron contamination → galvanic corrosion risk

Excessive grinding: Surface damage or introduction of micro-cracks

Long acid immersion: Hydrogen embrittlement risk

Chlorinated solvents: May form TiCl compounds or stress corrosion risk