152
Fundamentals of Corrosion
Water-repellent preservatives can also be used on bare wood prior to priming and painting or in areas where old paint has peeled, exposing bare wood.
This treatment prevents rain or dew from penetrating into the wood, particularly at joints and end-grain, thereby reducing the swelling and shrinking
of wood. This reduces the stress placed on the paint film, thus extending its
service life.
TabLE 4.24
Painting and Weathering Characteristics of Various Woods
Woods
Ease of Keeping
Painted
Resistance to
Weathering
Softwoods
Cedar
1
A
Cypress
1
A
Redwood
1
A
Pine, ponderosa
3
Β
Fir
3
Β
Hemlock
3
Β
Spruce
3
Β
Douglas fir
4
Β
Larch
4
Β
Hardwoods
Aspen
3
Β–Α
Basswood
3
Β
Cottonwood
3
D–B
Magnolia
3
Β
Yellow poplar
3
Β–Α
Beech
4
D–B
Birch
4
D–B
Gum
4
D–B
Lauan (plywood)
4
Β
Maple
4
Β
Chestnut
5–3
C–B
Walnut
5–3
C–B
Elm
5–4
D–B
Hickory
5–4
D–B
Oak, white
5–4
D–B
Oak, red
5–4
D–B
Note: 1 = easiest to keep well painted; 5 = most difficult. A = most
resistant to weathering; D = least resistant to weathering.
Source: From Reference 24.