When?
Where? How?
Hot
dip galvanizing is mainly used in corrosive environments, like corrosion
category 2 to 5 acording to
EN
ISO 12944-2, but can also be used in less severe environments, for example
indoors.
Below
advises about which types of surface coatings that can be used in different
environments are given.
An
comparement between their advantages and disadvantages are also shown.
COMPARISON
BETWEEN DIFFERENT ZINC COATING METHODS
|
Hot
dip galvanizing |
Electroplating
|
Zinc
spraying |
Coating
thickness |
70
- 215 µm |
3-
12 µm 1) |
40
- 200 µm |
Standard |
EN
ISO1461 |
ISO
2081 |
2972 |
Adherence |
Alloying
with the steel |
Electro-cemical |
Mechanical |
Application |
Dipping
in melt zinc |
Electrolytic
deposit |
Spaying
of molten zinc droplets |
Appearance |
Shiny
and/or gray |
Shiny |
Light
gray |
Finish |
Good |
Very
good |
Good |
Spread
in thickness |
Low |
Medium
2 |
Higher
3 |
Coating
inside cavities |
Yes |
No |
No |
Outdoor
protection 4) |
Very
good (25 - 75 years) |
Bad
(1 - 6 years) |
Good
(10 - 50 years) |
Quality
control |
Easy |
Easy
5 |
Easy
5 |
Upper
size limitation |
Around
25 m in Norden |
Around
6 m in Norden |
No
limits |
Lower
size limitation |
3
mm wood screw |
Approximately
2 mm |
Heavy
enough for the spray pressure. |
Use
of coated product |
Utedoor
when long lifte time is required |
Indoor
or outdoor during shorter periods |
Utdoor |
Life
time cost |
Very
low |
High |
Low |
Cathodic
protection |
Very
good |
Limitid |
Good |
Deformation
during application |
May
occur 6 |
No |
No |
1)
Thicker coatings may be created, but those will be more expensive to create
than corresponding hot dip galvanized coatings.
2) Depends on electrode positions.
3) Operator dependent.
4) Local variations may occur.
5) More mesurements are required.
6) Internal stresses in the steel may be relaxed in the
galvanizing bath.
|