Volume 8 – Mechanical and Electrical Services - Malaysia Geoportal
Volume 8 – Mechanical and Electrical Services - Malaysia Geoportal
Volume 8 – Mechanical and Electrical Services - Malaysia Geoportal
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Chapter 2 GATE DESIGN<br />
Corrosion mitigation can be accomplished by design considerations, by employing corrosion-resistant<br />
materials of construction, by employing cathodic protection <strong>and</strong> by application of protective coatings.<br />
Selection of type of corrosion protection is dependent on the particular environment in which the<br />
gate will operate.<br />
Design Consideration<br />
The use of acceptable engineering practices to minimise corrosion is fundamental to corrosion<br />
control. Avoid crevices where deposits of water-soluble compounds <strong>and</strong> moisture can accumulate<br />
<strong>and</strong> are not accessible for maintenance. Any region where two surfaces are loosely joined, or come<br />
in close proximity is also considered as a crevice. Jointing practices such as bolting, back-to-back<br />
angles, rough welds, sharp edges, corners <strong>and</strong> intermittent wells also create corrosion problems<br />
Protective Coating Systems<br />
Application of coating systems is the primary method of corrosion protection for gates. Coating<br />
systems include alkyd enamel, vinyl <strong>and</strong> epoxy paint systems. Painting system should follow<br />
accepted procedure as recommended by paint manufacturers to ensure good corrosion protection.<br />
The painting procedure would normally include proper surface preparation by s<strong>and</strong> blasting to SA<br />
2.5, Cleaning of surface to remove residues, coating with primer <strong>and</strong> at least two finishing coats to<br />
the recommended thickness.<br />
A typical recommended painting scheme for steel works is as follows:-<br />
1 st coat Epoxy Primer DFT 50 micron<br />
2 nd coat Coaltar Epoxy DFT 100 micron<br />
3 rd coat Coaltar Epoxy DFT 50 micron<br />
For hot dip galvanizing protection, BS729 shall be adhered to as follows:-<br />
Material thickness<br />
more than 5mm<br />
less than 2mm<br />
Min. coating weight<br />
610 g/m² (100 micron)<br />
335 g/m²<br />
Metalic coatings such as thermal sprayed (metallizing) zinc, aluminium, aluminium-zinc alloys,<br />
stainless steel <strong>and</strong> chromium can be used to protect against corrosion or provide increase wear <strong>and</strong><br />
abrasion resistance <strong>and</strong> should be considered in extreme abrasive environment. Zinc-rich coatings<br />
are widely used to provide galvanic corrosion protection to steel.<br />
Cathodic Protection<br />
Cathodic protection is often used in the more corrosive environment to supplement the paint<br />
coatings. Cathodic protection is achieved by applying a direct current to the gate from some outside<br />
source by impressed current or sacrificial anode attached to the gate. Cathodic protection introduces<br />
a low current to counteract the continuous process of removing electrons from the steel.<br />
2.5 GATE INSTALLATION<br />
The gate assembly is a custom made equipment comprising various parts, components <strong>and</strong><br />
accessories such as gate, guide, lifting mechanism etc. Being custom made to order on an individual<br />
basis, complete inter-changeability of all parts is not possible <strong>and</strong> as such it is essential that the<br />
equipment is carefully h<strong>and</strong>led during transit, unloading, storage <strong>and</strong> installation to avoid damage or<br />
mixing up. (Refer Appendix 2A for a sample Method Statement on Gate Installation)<br />
2-24 March 2009
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