Galvanization or galvanizing is the process of applying a protective 1.____zinc coating to steel or iron, to prevent 2.____.
- Zinc
2. Rusting
The most common method of Galvanizing is?
Hot Dip Galvanizing.
Hot Dip Galvanizing is the process of?
Submerging parts in
a molten both of hot Zinc.
Electro-galvanization is often confused with “Galvanizing” however, it is a different process which?
Electroplates a metal with a thin layer of Zinc. It is sometimes preferred.
Why would Electro-galvanizing be preferred over actual galvanizing?
- Thinner zinc layer. Thicker layers, such as those with Hot Dipping, can interfere with thread sizing for bolts/screws.
- Brighter, prettier, coating/zinc layer.
Zinc Whiskers are a 1.___ ___ that is believed to be more prevalent with 2.___ ___ than with 3.___ ___ ___. This can be a greater area of concern with electrical boxes due to the risk of short circuits.
- Stress Phenomenon
- Electro-Galvanization
- Hot Dip Galvanizing.
Galvanizing protects the underlying Steel or Iron in three main ways. These are?
- Protects corrosive substances from reaching the underlying metal. (Barrier).
- By corroding preferentially. (I.e. Before the underlying metal.) (Cathodic)
- If the barrier protections fails, and the underlying metal has been exposed, zinc can still protect that exposed metal from rusting if there is Zinc close enough to the bare spot to be electrically coupled. If all the Zinc in the immediate area is consumed by corrosion then localized corrosion of the base metal can occur.
Due to the Cathodic protection of Zinc; The application of 1.____ over Zinc is seen as industrial standard.
- Chromates
Galvanizing can be 1. ___ ___ by using a 2. ___ ___. Which is using a 3. ___ or ___ ___ over hot-dip galvanized steel. Though it is usually more common to see a coating applied over 4. ___ ___.
- Painted over.
- Duplex System.
- Paint or Powder coating.
- Electro Galvanizing.
The most common method of Galvanizing is?
Hot Dip Galvanizing.
Hot Dip Galvanizing does not generally reduce the strength of metals on a measurable scale. With the exception of high strength steels (those with 1. ___ ___) where 2. ___ ___ can become a problem.
- 1100 Mega pascal (MPa)
MPa is a system used to denote pressure. Or the amount of pressure an object can withstand.
1,100 MPa = 11,000 Bar.
Hot Dip Galvanizing does not generally reduce the strength of metals on a measurable scale. With the exception of high strength steels (those with 1. ___ ___) where 2. ___ ___ can become a problem.
This deficiency should be a consideration when manufacturing high-stress products.
- 1100 Mega pascal (MPa)
- Hydrogen Embrittlement.
MPa is a system used to denote pressure. Or the amount of pressure an object can withstand.
1,100 MPa = 11,000 Bar.
Galvanizing is not suitable for exposure to 1. ___ ___ such as 2. ___. Or environments where those things are common. Such as an environment where 3. ___ ___ is possible and/or common.
- Corrosive Materials.
2. Acids
For Bolts and Nuts of 1. ___ or smaller, the HDG fills in too much of the threads. So the dimensions of the threads must be reduced during manufacturing to allow for the additional thickness of the applied Zinc layer. For this reason it isn’t common to use HDG on threads of 1. ___ or smaller.
- 3/8” or smaller.
The Spangled appearance of Galvanizing is caused by visible 1. ___.
By varying number of particles added for heterogeneous nucleation and the rate of 2.____ in HDG the Spangle can be adjusted from an apparently uniform surface (no small to see with the naked eye) to several centimeters wide.
- Crystallites.
2. Cooling.
Diffusion is?
- The intermingling of substances by the natural movement of their particles. Example: The rate of diffusion of a gas”
- A physical process that refers to the net movement of molecules from a region of high concentration to one of lower concentration. … For instance, a gas diffuses very quickly in another gas. An example of this is the way the noxious smell of ammonia gas spreads in air.
Nucleation is?
The initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapor, in which a small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid, forming a site upon which additional particles are deposited as the crystal grows
Such as salt crystals forming in water that has cooled from boiling. As the water boiled, the salt was dissolved and no longer visible. As the water cools the salt undergoes Nucleation to form salt crystals.
What is the difference between Heterogeneous nucleation and Homogeneous nucleation?
Heterogeneous nucleation occurs at nucleation sites on surfaces in the system.
Homogeneous nucleation occurs away from a surface.
The terms Vapor Galvanizing, Thermal Diffusion Galvanizing, and Dry Galvanizing are nicknames for?
Sherardising.
Sherardising, unlike HDG, uses steel parts up to 1. ___ in a closed rotating drum that contains 2. ___ ___ ___ and possibly an 3. ___ ___ such as sand.
At temperatures above 4. ___ the 2. ___ ___ ___ evaporates and diffuses into the steel substrate forming diffusion bonded Zn-Fe-phases.
- 932 F
- Metallic Zinc Dust
- Inert Filler
- 572 F
Zn is?
Zinc as shown on the Periodic Table.
Fe is?
Iron as shown on the Periodic Table.
With Sherardising: if the metal surface is free of 1. ___ or ___, no pretreatment is needed.
- Scales or Oxides
With Sherardising: The process is 1. ___ ___, so 2. ___ ___ is prevented.
- Hydrogen Free
2. Hydrogen Embrittlement.
