1. Crevice corrosion: Titanium rod manufacturers pointed out that crevice corrosion is a local corrosion phenomenon that occurs in close gaps. The gaps can be caused by structures (such as flange connection surface or gasket surface, tube and tube sheet expansion joint, and The connecting surface of bolts or rivets, etc.) can also be caused by scaling or deposits under the covering surface. In the early days, it was believed that titanium did not undergo crevice corrosion at all in seawater and salt spray. Later, in high-temperature chloride medium (such as seawater heat exchanger), wet chlorine gas (such as wet chlorine gas tube condenser), oxidant corrosion inhibition hydrochloric acid solution In media such as formic acid and oxalic acid solution, crevice corrosion damage of equipment has occurred successively.
The crevice corrosion of titanium rods is related to many factors such as environmental temperature, chloride type and concentration, pH value, and the size and geometry of the crevice. In addition, the crevices composed of titanium and nonmetals such as polytetrafluoroethylene, titanium and asbestos are more sensitive to crevice corrosion than those composed of titanium and titanium.
2. Pitting corrosion: Pitting corrosion is a form of corrosion peculiar to passivated metals. Compared with stainless steel or aluminum alloy, the pitting corrosion resistance of titanium is very excellent. Due to the increasing application of titanium in high-temperature concentrated chloride solutions, the number of pitting corrosion cases of titanium equipment has gradually increased.
The titanium anode basket in electrolytic zinc, the titanium coil heated in zinc chloride solution, and the titanium ball valve of 72% calcium chloride solution at 175℃ have all experienced pitting corrosion damage. Generally speaking, pitting corrosion of titanium is more difficult than crevice corrosion, which usually appears in the form of pitting corrosion on the crevice surface.
3. Galvanic corrosion: Galvanic corrosion is a phenomenon in which dissimilar metals contact in the electrolyte solution (including electrical contact). Due to the difference in the steady-state potential of the metal, one metal accelerates the corrosion of another metal (ie, anode dissolution). The oxide film of titanium is very stable and is generally in the cathode state, and galvanic corrosion will not accelerate the anode dissolution of titanium.
However, attention must be paid to the hydrogen absorption of titanium in the cathode state, which will eventually lead to hydrogen embrittlement. At the same time, it is necessary to prevent the accelerated corrosion of the coupling metal (such as aluminum, copper, zinc, etc.). The size of the galvanic corrosion of the metal depends on the difference of the galvanic sequence of the coupled metal in the medium.
titanium bar High Quality Titanium Wire titanium welded pipe titanium rolling sheet
The crevice corrosion of titanium rods is related to many factors such as environmental temperature, chloride type and concentration, pH value, and the size and geometry of the crevice. In addition, the crevices composed of titanium and nonmetals such as polytetrafluoroethylene, titanium and asbestos are more sensitive to crevice corrosion than those composed of titanium and titanium.
2. Pitting corrosion: Pitting corrosion is a form of corrosion peculiar to passivated metals. Compared with stainless steel or aluminum alloy, the pitting corrosion resistance of titanium is very excellent. Due to the increasing application of titanium in high-temperature concentrated chloride solutions, the number of pitting corrosion cases of titanium equipment has gradually increased.
The titanium anode basket in electrolytic zinc, the titanium coil heated in zinc chloride solution, and the titanium ball valve of 72% calcium chloride solution at 175℃ have all experienced pitting corrosion damage. Generally speaking, pitting corrosion of titanium is more difficult than crevice corrosion, which usually appears in the form of pitting corrosion on the crevice surface.
3. Galvanic corrosion: Galvanic corrosion is a phenomenon in which dissimilar metals contact in the electrolyte solution (including electrical contact). Due to the difference in the steady-state potential of the metal, one metal accelerates the corrosion of another metal (ie, anode dissolution). The oxide film of titanium is very stable and is generally in the cathode state, and galvanic corrosion will not accelerate the anode dissolution of titanium.
However, attention must be paid to the hydrogen absorption of titanium in the cathode state, which will eventually lead to hydrogen embrittlement. At the same time, it is necessary to prevent the accelerated corrosion of the coupling metal (such as aluminum, copper, zinc, etc.). The size of the galvanic corrosion of the metal depends on the difference of the galvanic sequence of the coupled metal in the medium.
titanium bar High Quality Titanium Wire titanium welded pipe titanium rolling sheet
No comments:
Post a Comment