Guidelines for Tantaline® treatment



Tantaline's Tantalum Surface Alloy for corrosion protection depends on a fully intact tantalum surface alloy on your parts. Attention to weld and fabrication quality must be made prior to shipping your parts.

Weld quality:

All welds must be free of voids and defects and must be ground smooth to remove any burrs. For parts where the internal surface is critical, welds must be made to avoid crevices and have complete penetration to the internal surface. We recommend when possible the welds be made internally and externally to create the best internal surface quality. If an internal weld is not possible the weld must be made such that the root of the weld fully penetrates to the internal surface and no voids, gaps or defects are formed. All welds must be able to pass a dye penetrant test according to ASTM E165 standards.

Surface roughness and morphology:

Parts may be shipped with ground, machined or polished surface as long as they are burr free.  Parts may be prepared in different ways (e.g. by grinding, polishing, glass bead blasting, vibration polishing, chemical etching or electrochemical polishing) to remove burrs. A rule of thumb for completion is feeling a smooth surface when sliding a soft cloth over the surface.

Edges and corners:

Edges and corners should be burr free and as a minimum be rounded to a radius larger than 0.25 mm / 0.01 in. Preferable edges should rounded to be softer than 0.5 mm (1/64 in).


Holes open on both sides should in general maintain a minimum diameter to length ratio of 1:10.  For holes open only on 1 side the minimum diameter to length ratio is 1:5. Longer holes may be processed in special setup (contact Tantaline)

Straight Threads:

Be specifically aware to remove any burrs, laps or crests on threads. On bolt / nut (or tapped hole) pairs it is preferable to have the threads oversized on the nut (or tapped hole) by 0.016" to accomodate the increase in thickness due to the Tantaline process. For Tantaline treated threaded parts that will not be mated to another Tantaline treated threaded part it is preferable to have the thread over or undersized by 0.008".

Casting quality:

All casts must be free of voids and defects both internally and externally. All burrs and surface defects must be ground smooth. Casts should have any contamination of foreign metals or casting byproducts. It is preferable to supply investment cast products. Tantaline reserves the right reject castings not meeting these requirements.

Joints & crevices:

Product should have no crevices or gaps to bridge (Exampe: Pressed pins, abutted surfaces). If crevices do exist they must be seal welded.  For parts joined by threads, those threads must be Tantaline treated before threading.


The customer must be sure to deliver parts in the cleanest possible condition (i.e. free of paint, oil and other process chemicals). Tantaline does a pre-treatment including ultrasonic cleaning, degreasing and pickling. The pretreatment is done in order to remove light (non-industrial) contamination. Residual greases and oils from machining in customer workshops may, is the customers responsibility to clean.  Please be aware of the following issues:

  • Parts should be free of paint, oil, grease, fat, lubricants or other metal working chemicals (we kindly ask you to consult your supplier for a suitable cleaning procedure to be performed before shipping to Tantaline).
  • Parts should be free of dust, dirt, metal particles, abrasives (e.g. from grinding or cutting) or polishing agents.
  • Special attention must be drawn to rinse holes, grooves or concave geometries, since contaminants tend to concentrate in these areas.
  • Beware to avoid silicone containing cleaning agents (typically found in cleaning products used for home/household cleaning). Silicone is almost impossible to remove subsequently.
  • Parts must be dried after the cleaning. We recommend that last cleaning step involve rinsing/flushing in clean (fresh/new) alcohol (ethanol) or clean (fresh/new) acetone and drying in hot air to remove any water from previous cleaning steps.
  • Keep the areas to be Tantaline treated as clean as possible. Avoid to write (e.g. with markers) and do not use tape in these areas. If you need to use tape for protection, you may wrap the pars into a thin plastic film (plastic shrink wrap) before taping.
  • Parts should be packed in clean closed (or folded) bags to avoid contamination of particles during transport. Larger amount of parts can be shipped in boxes supplied with a sealing lid.
  • If you cannot avoid lubricating parts (e.g. non-stainless steel parts), due to risk of rust/corrosion during shipping, please include a reference for the oil and a description of how the oil is removed.



  • Chemical process
  • Oil & Gas
  • Pharmaceutical
  • Semiconductor
  • Mining
  • Marine
  • General Industrial
  • Hot acids, strong acid leaching & strong acid etchants
  • Acid gases (CO2, SO2, H2S) in vapor phase, sour gas compounds
  • Wet and dry chlorine (Cl), corrosive sea water with chlorinated compounds & oxidizing agents
  • Pressure oxidation, alkylation, nitration
  • Byproducts of silicon deposition
  • Ammonia and amine derivatives
  • Agitators, stirrers, mixers, & impellers
  • Valves
  • Bellows
  • Rupture disc holders
  • Fittings
  • Fasteners
  • Glass repair kits
  • Pumps, seals, couplings
  • Thermowells, sensors, flowmeters
  • Autoclaves and lab reactors
  • Heat exchangers
  • Tweezers


  • Hydrofluoric acid (HF) and fluorinated compounds
  • Fuming sulfuric acid (Oleum)
  • Mineral acids beyond 250°C
  • Strong base/alkaline media having pH > 12
  • Air > 300 °C
  • Wear components
  • Large size components
  • Porous castings