passive film

localized corrosion

titanium

micro-arc oxidation

laser surface

corrosion behavior

corrosion behaviour

laser melting

Materials & design

• Corrosion behavior of laser powder bed fusion produced Ti–6Al–4V samples was investigated. • Static and dynamic Hank’s solutions were selected as the corrosion environments. • Flow solution degrades passive film of sample and thereby the corrosion resistance. • Flow solution promotes the deposition of calcium phosphate and hydroxyapatite. The corrosion behavior of laser powder bed fusion produced (L-PBF-produced) titanium alloys involving flowing body fluid is still unclear. Therefore, this work investigates in vitro corrosion behavior and the characteristics of passive films formed on L-PBF-produced Ti–6Al–4V in both static and dynamic Hank’s solutions. Electrochemical measurements, immersion tests, X-ray photoelectron spectroscopy and scanning electron microscopy were conducted. In comparison to the L-PBF-produced Ti–6Al–4V in static Hank’s solution, the samples showed lower charge transfer resistance and higher passivation current density (anodic current density as well) in dynamic Hank’s solution. Meanwhile, a more apparent deposition of apatite and hydroxyapatite is found on the L-PBF-produced Ti–6Al–4V in dynamic Hank’s solution. Such outcomes mainly result from the enhancement of film/solution interfacial transportation in dynamic Hank’s solution. The dynamic Hank’s solution provides more calcium and phosphate ions to the surface of the passive film and also takes away the dissolved metal ions. Therefore, more salt deposition and a lower-quality passive film are found.

Corrosion behavior and characteristics of passive films of laser powder bed fusion produced Ti–6Al–4V in dynamic Hank’s solution