ASTM B600 is the standard guide for descaling and cleaning titanium and titanium alloy surfaces. This guide covers a cleaning and descaling procedure for the removal of ordinary shop soils, oxides, and scales from the surface of titanium or titanium alloy surface. The soils, oxides and scales are resulting from heat treatment operations, manufacturing processes, or foreign substances present as surface contaminants. They may have very negative effects on the corrosion resistance, stability and quality of the finished titanium products, thus, shall be removed prior to chemical milling, joining (welding), plating, and fabrication.

Processing Soil Removal

As recommended & prescribed in Section 2 of ASTM B600, the “soil”, such as grease, oil and lubricants, shall be removed by alkaline or emulsion soak-type cleaners and electrolytic alkaline cleaning systems. The removal of soil shall be the first step prior to any further process. Spark discharge and subsequent pitting shall be avoided in electrolytic systems.

Blast Cleaning

ASTM B600 has provided three mechanical descaling methods including sandblasting, shot blasting, and vapor blasting. The blasting procedure will remove hot work scales and lubricants from titanium surfaces. It is usually followed by molten alkaline conditioning and acid pickling process. The sand selection, roughening of exposed surfaces, removal of embedded steel blasting particles, and residual stresses are all discussed.

Pickling, Cleaning and Descaling

As blasting cleaning may not remove titanium surface contaminants completely, post treatments are required. ASTM B600 has classified these post treatments as:

• Conditioning: to remove scale and lubricant residues completely prior to final pickling. The conditioning methods include proprietary caustic-based solution immersion, molten alkaline-based salt baths at different temperature, removal of oxides and heat tints by pickling in an nitric acid & hydrofluoric acid combined solution, removal of scale mixed with graphitic or glass-type lubricants in a molten alkaline-based salt bath, removal of complex scales mixed with graphitic and molybdenum disulfide lubricants.
• Acid Pickling: following the mechanical abrading or chemical conditioning, the titanium material shall be further treated by acid pickling and final cleaning to obtain completely clean surface. The pickling procedure may involve the using of sulfuric acid or nitric acid+hydrofluoric acid solutions.
• Final Cleaning: To ensure complete removal of metallic iron and other surface contaminants, the final cleaning utilizes nitric acid or citric acid to immerse the titanium work within specified temperature range for the specified time.

Inspection

Visual inspection, hydrogen absorption monitoring during the cleaning process, and cleanliness evaluation by chemical milling test are discussed.

PDF Download of ASTM B600 – 2011 (R2017)

Click to download the PDF of ASTM B600 – 2011 (Reapproved 2017). This is the newest revision of B600 which is updated in 2017 by ASTM.