Steel Construction Vol 40 No 4 - Metal Cladding and Light Steel Frame | Page 12

SAISC TECHNICAL
Grades of material are now described,
in line with international practice, by
minimum yield strength measured in megapascals (MPa). CQ has become 230 and
fullhard 550. An intermediate grade of 300
MPa has been introduced. Unfortunately
there is no uniformity in the prefix used
to describe the grades e.g. G550, ISQ500

‘‘

The extremely high levels
of UV radiation experienced
in Southern Africa quickly
reveal the quality of the
pigments and resins used. It is
therefore advisable to specify
brands with a proven track
record rather than accept an
unproven paint system.

10 Steel Construction Vol. 40 No. 4 2016

etc. generally material up to and including
0.53/5mm is 550 MPa, 0.55/8 is 300MPa
and thicker material 230MPa.
Thickness is the total coated thickness
of the coated material (steel core plus
coating) rolled to a tolerance of ±0.02mm.
Certain unscrupulous roll formers are
substituting 0.48mm material for 0.50mm
etc. In an attempt to address this problem
the National Regulator for Compulsory
Specifications has agreed that the shortly
to be published revision to SANS 10400
Part-L will require: all coil used for the
manufacture of metal cladding to be
indelibly marked 50mm in from each
edge and at not more than three metre
intervals, with amongst other data
the weight and type of any metallic
coating and identification of any other
coating applied to the coil. Local cladding
manufacturers refer to this indelible
marking as branding.
A large portion of the population are not
aware that galvanized (or more correctly
zinc coated) material is available with
different thicknesses of the coating ranging
from Z100 to Z600. The Z denotes the
coating is zinc and the number the total
mass of the coating, measured in grams, to
both sides of a square metre of material.
As the durability of a coating is basically
proportional to thickness a Z275 coating
will have a service life expectancy 2.75
times that of a Z100 coating. Zincalume,
ZincAL and Aluzinc (which has effectively
become a generic name) are all copyrighted
names for 55% aluminium-zinc coatings.
Similar to zinc coatings they are available
with different thicknesses of the coating
ranging from AZ100 to AZ200 with
durability being proportional to thickness.
There are other aluminium-zinc coatings
available with the percentage aluminium
varying from as low as 5%. These coatings
are normally denoted as ZA. Colour coated
(pre-painted) material is available with
either a galvanized or 55% aluminim-zinc

coated substrate. The overall performance
of these products in a given environment
is dependent on the combination of paint
system, the thickness of individual layers
plus type and thickness of the underlying
metal coating. Not all paint systems are
equal. Performance of paints is directly
linked to their formulation plus quantity
and quality of the ingredients used.
Paint systems with the same formulation
composed of lesser quantity and quality of
materials will not have the same durability
as those made with better quality materials.
The extremely high levels of UV radiation
experienced in Southern Africa quickly
reveal the quality of the pigments and resins
used. It is therefore advisable to specify
brands with a proven track record rather
than accept an unproven paint system.
Prior to the RSA becoming a member
of the World Trade Organization (WTO)
cladding products available locally were
comparable, however, that is no longer the
case. Our market is being flooded with
inferior materials and products where price
is considered over performance. When
considering the life cycle of products never
has the expression penny wise, pound
foolish been more relevant.
The growing incidence of counterfeit
documents pertaining to quality and
composition of materials is cause for
concern. We therefore encourage the
insistence of branded materials as a means
of ensuring the components supplied are
what were specified.
Branded coil has been available in the RSA
for over fifteen years, mainly as an option to
the more reputable cladding manufacturers.
Fortunately two local and one foreign mill
have adopted a policy of supplying branded
product only. In addition to the minimum
data detailed above their branding contains
the name of the producer mill, production
date and batch number.