Titanium rod is corroded the reason and the form!

Release time：2022-03-23 14:04:47 丨 Number of visits：

We generally think that titanium and titanium alloy products are not easy to be corroded, but there are often titanium rod corrosion phenomenon on the market, how is this? Today, xiaobian will briefly introduce the causes and main forms of titanium rod corrosion for you. I hope you can avoid titanium rod corrosion in use.

1. Gap corrosion: gap corrosion is a local corrosion phenomenon occurring in the tight gap position. The gap can be caused by the structure (such as flange connection surface or gasket surface, tube and tubesheet expansion and bolt or rivet connection surface, etc.), but also caused by scaling or sediment coverage. In the early stage, titanium was considered to have no gap corrosion in seawater and salt fog. Later, gap corrosion of equipment occurred successively in high temperature chloride medium (such as seawater heat exchanger), wet chlorine gas (such as wet chlorine tubular condenser), oxidizer corrosion inhibiting hydrochloric acid solution, formic acid and oxalic acid solution and other media.

The gap corrosion of titanium rods is related to many factors such as ambient temperature, chloride type and concentration, pH value, and the size and geometry of the gap. In addition, the cracks composed of titanium and ptfe, titanium and asbestos are more sensitive to gap corrosion than those composed of titanium and titanium.

2, point corrosion: point corrosion is a unique form of passivation metal corrosion. The pitting resistance of titanium is very excellent compared with stainless steel or aluminum alloy. Due to the increasing application of titanium in high temperature concentrated chloride solution, the pitting corrosion cases of titanium equipment are increasing gradually.

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

3, galvanic corrosion, galvanic corrosion are dissimilar metals in contact in electrolyte solution (including electric contact), due to differences in the steady-state potential of metals, cause a kind of metal to speed up another kind of metal corrosion (i.e., anodic oxidation) phenomenon of titanium oxide film is very stable, generally will always be in a state of cathode, the galvanic corrosion will not speed up the anodic dissolution of titanium.

Titanium rod manufacturers believe that attention must be paid to the hydrogen absorption of titanium in the cathode state and ultimately lead to hydrogen embrittlement, and at the same time, it is necessary to prevent the accelerated corrosion of the coupling metal (such as aluminum, copper, zinc, etc.). The galvanic corrosion of metal depends on the difference of galvanic sequence of the metal in the media.