1. Electroplating
Principle:
Like "painting" metal, a metal film is plated on the surface by electrolysis, which can prevent rust, resist wear and become beautiful.
Function:
1. Wear resistance: Nano-pure nickel is plated on the surface of Ti6Al4V
Titanium Alloy, and the hardness and wear resistance are increased;
2. High-temperature anti-stuck skills: After the titanium blades are silver-plated, they will not be "welded" together even if they are rubbed at a high temperature of 500℃. The "bite problem" of aircraft engines is solved by it.
Difficulty: Titanium is too easy to "make friends" with oxygen, and there is always a layer of oxide film on the surface, which will mess up during electroplating.
Solution:
1. Use nickel sulfate electrolyte and activator, first use electric pulse to "activate" the titanium surface, and then plate nickel.
2. Use hydrofluoric acid + dimethylformamide solution to corrode the titanium surface, and copper plating directly can also stick very firmly.
2. Micro-arc oxidation
Principle:
A ceramic film is "burned" on the titanium surface by high-voltage electric sparks, which is mainly composed of titanium oxide.
Function:
1. The ceramic film and the titanium substrate bite like tree roots into the soil, and will not fall off even if the hydraulic press is pressed to 200 MPa.
2. The film is several hundred microns thick, as hard as ceramic, corrosion-resistant, wear-resistant and heat-resistant.
Customization:
Adding potassium permanganate to the electrolyte can make a titanium film that is both corrosion-resistant and antibacterial!
3. Electrophoretic coating
Principle:
Put the titanium parts into the charged paint water, and the paint particles will "queue up" to attach to the surface to form a paint film.
Advantages:
1. Non-toxic, water-soluble, more environmentally friendly than traditional spray painting.
2. High degree of automation, 90% of car bodies are primed with this method.
3. Good biocompatibility, such as TA4 titanium alloy coated with polyurethane, can be used in the medical field.
Little knowledge:
Cathode electrophoresis is more powerful than anode, with stronger anti-corrosion and covering capabilities.
IV. Anodic oxidation
Principle:
It is equivalent to the reverse operation of 3D printing for metals. Titanium is used as the anode and energized to grow an oxide film in the electrolyte. It is divided into two forms:
1. Dense type: tens to hundreds of nanometers thick, smooth and dense, good biocompatibility, suitable for corrosion protection and medical use.
2. Porous type: It can grow into TiO₂ nanotube arrays in fluorine-containing electrolytes, like countless nano straws arranged.
Magical applications:
1. Nanotubes have a large specific surface area and can be used as photocatalytic materials (decomposing pollutants) and solar panels.
2. Made into hydrogen-sensitive sensors, they are super sensitive to hydrogen, with fast and stable response.
3. Used in lithium batteries, they can prevent corrosion and improve charging and discharging efficiency.
