What are the corrosion forms of titanium rods?

1. Crevice corrosion: titanium rod manufacturers point out that crevice corrosion is a local corrosion phenomenon occurring in the close gap position. The gap can be caused by structure (such as flange connection surface or pad surface, tube to tubesheet expansion joint, bolt or rivet connection surface, etc.), or it can be caused by scaling or covering surface under deposition. In the early stage, it was thought that there was no crevice corrosion of titanium in sea water and salt spray. Later, crevice corrosion of equipment occurred in high temperature chloride medium (such as sea water heat exchanger), wet chlorine gas (such as wet chlorine tubular condenser), hydrochloric acid solution with oxidant corrosion inhibition, formic acid solution and oxalic acid solution. The crevice corrosion of titanium rods is related to many factors, such as ambient temperature, chloride type and concentration, pH value, size and geometry of cracks. In addition, the crevice composed of titanium and polytetrafluoroethylene, titanium and asbestos is more sensitive to crevice corrosion than that of titanium and titanium.

2. Pitting corrosion: pitting corrosion is a unique corrosion form of passivated metals. Compared with stainless steel or aluminum alloy, the pitting corrosion resistance of titanium is excellent. Due to the increasing application of titanium in high temperature concentrated chloride solution, the pitting corrosion of titanium equipment increases gradually.

The pitting corrosion of titanium anode basket in electrolytic zinc, titanium coil heated in zinc chloride solution and titanium ball valve in 72% calcium chloride solution at 175 ℃. Generally speaking, pitting corrosion of titanium is more difficult than crevice corrosion, and crevice corrosion usually occurs in the form of pitting corrosion on the crevice surface.

3. Galvanic corrosion: galvanic corrosion refers to the phenomenon that dissimilar metals contact (including electrical contact) in electrolyte solution. Due to the difference of steady-state potential of metals, one metal accelerates the corrosion of another metal (i.e. anodic dissolution). The oxide film of titanium is very stable and is always in the cathode state. Galvanic corrosion will not accelerate the anodic dissolution of titanium.