Surface Technology - 230317

Question 1

Advantages of nickel coating

Answer 1

decoration, wear resistance

Question 2

Mechanical properties nickel coating with low PH (1-4)

Answer 2

LOW: hardness, stress, tensile strength. HIGH: elongation

Question 3

Mechanical properties nickel coating with high PH (5-6)

Answer 3

HIGH: hardness, stress, tensile strength. LOW: elongation

Question 4

How do you get the best quality in the edges?

Answer 4

chemistry: better edges, better appearance, Electro: low quality in the edges

Question 5

In what stage of the process should you do the coating of a piece?

Answer 5

coating before, as early as possible, thermal treatment after the coating

Question 6

Advantages of galvanizing (zinc coating)

Answer 6

1. abundant mineral (cheap)
2. galvanized steel is fully recycable (no losing of physical or chemical properties)
3. zinc corroted layer (whiterust) is also protective, decades of protection

Question 7

stages of galvanizing

Answer 7

Surface preparation (degreasing, mild acid). Galvanizing, (dipped into molten zinc), chemical reactions between zinc and iron in steel.

Question 8

What are the critical parameters in the process?

Answer 8

steel temperature, zinc temperature

Question 9

What is better for welding?

Answer 9

Zinc iron in the middle, iron is always good for welding.

Question 10

Aluminum welding

Answer 10

It was not possible to assure that the welding points will work. Welding point of aluminum lower than steel, aluminum high thermal conductivity, difficult to control that the high energy will be concentrated in one point. Now, short time, high energy and this solves the welding problem.

Question 11

Aluminum painting or steel painting

Answer 11

Primer is always needed.

Question 12

Most difficult part for corrosion of a car

Answer 12

When it rains, some water goes inside the door since the glass is not sealed completely (it can open).

Question 13

Typical zinc thicknesses

Answer 13

100 microns of zinc, streetlights, motorway signals. 10 microns of zinc, automotive industry for appearance.

Question 14

Corrosion intensity as a function of the environment

Answer 14

Indoor, country, Urban, Marine, Industrial (it grows)

Question 15

Main cause of corrosion

Answer 15

Salt + water. In winter countries: salt to avoid slipping. In warm countries: The seawater.

Question 16

Two different types of corrosion

Answer 16

Dry corrosion: oxygen. Wet corrosion: acid, base, water + salt.

Question 17

Possible uses of PVD

Answer 17

Physical Vapor Deposition: Improves conductivity and has a lot of uses in Electronics. Gold coating.

Question 18

When is a good idea to choose an organic coating?

Answer 18

When the material is not weldable, you paint it and it will get protected.

Question 19

What is the Daniell-Element electrochemical cell?

Answer 19

Anode: Zinc and zinc sulfate, eventually dissapears. Gives electrons.
Cathode: Copper and copper sulfate, receives electrons.
Converts chemical energy into electrical energy.

Question 20

Steel high UTS vs. Low UTS (Zufestigkeit)

Answer 20

High: brittle, expensive. Low: ductile and absorbs energy, allowing damage and not transmitting it to the passengers.

Question 21

Typical thicknesses for sheet metals

Answer 21

Car: 1mm sheets
Buildings: 10mm thickness

Question 22

Typical processes for Zinc coating

Answer 22

Electrocoating: precise, good elongation.
Dripping: huge parts, buildings and machines.