Surface Coating of Iron Castings
The most of iron castings need surface
coating to prevent rust. According to the different functions, there
are many types of surface coatings. According to our experience of
Dandong Foundry, we briefly
introduce some main coatings for castings.
1. Primer anti-rust painting
In order to prevent the rust during
shipping, normally, iron foundries
will paint the anti-rust primer painting for iron castings. These
paintings are very normal, so the prices are very low, it is about
30 USD/ton based on the total weight of castings.
2. lead-free (nonleaded) anti-rust painting
Normal primer painting has some content of lead, which will cause
the pollution to the underground water. Therefore, some iron
castings need lead-free painting. Lead-free painting is more
expensive than normal primer painting, so they are not widely used
except for the special uses.
3. RAL painting
RAL painting means the painting lives up with the RAL standard and
requirement to the colors. You need to buy these painting from
professional painting suppliers. Therefore, their cost is higher
than normal painting. RAL painting is for the finish painting, not
for primer painting.
4. Zinc-rich primers
Zinc-rich primer paintings have many advantages, such as quick
drying, good physical properties, good anti-heat property and can be
mixed to proper colors. Of course, zinc-rich primers are very
expensive, it is about 150 USD/ton. So, it is not commonly used.
5. Polyurethane Coating
PU (Polyurethane) Coating has good durability and good surface
flexibility. Its cost is about 150 USD/ton based on the normal
casting weights. Not commonly used.
6. Electro Galvanizing
This kind of galvanize is also normally
called as zinc plating. It is about 80 to 120 USD/ton according to
the difference of surface areas. Electro galvanizing is commonly
used for the high anti-rust requirements.
7. hot dip galvanizing
Hot dip galvanizing is also called hot galvanizing, or called HDG,
which is a kind of chemical galvanizing process. HDG has very good
anti-rust properties, it can prevent the iron castings from rust for
several years in the sea water. Since HDG has pollution and can
consume more zinc, so its cost is high, it is about 230 USD/ton.
8. heat resistance paint
heat resistance paint is also called as fire-resisting paint, which
is normally used for the stove parts. Since they need to resist
hundreds of degrees heat, so they are more expensive than normal
painting. It is about 220 USD/ton. Not cheap!
9. asphalt paint, bituminous paint
Bituminous paint is also called as asphalt paint, which is usually
used for the pipe lines and fittings, or marine parts. Normal
bituminous paint is not expensive, which is almost same as the
normal anti-rust painting. However, many overseas clients will
require the environmental bituminous paint. So, this kind of paint
will be more expensive, it is about 60 to 70 USD/ton.
Besides, there are many other surface coatings for iron castings,
such as electrophoresis coating,
chrome-plating, powder coating, emulsion paint etc. We can
not list all of them herein.