Why do gates rust?
All carbon based steels will rust if it comes into contact with water (rain). Water corrodes the metal leaving a rust deposit. This will start to happen as soon as the metal gets wet. If steel has been welded, the welded part is more porous than steel and water will get into the metal through the welds.
Can I prevent rust?
The only way to completely stop gates and railings from rusting is to have them galvanised in a special galvanising plant. This is a hot zinc dip which coats the metal completely and provides an air tight and durable seal. This is silvery in colour which fades over time. Galvanised items can be painted. If all the paint wears off and they are never painted, they will still not rust. Typically, galvanising might account for 20-25% of the cost of a gate so galvanised gates will always be more expensive than non galvanised gates. Galvanising is priced on weight, so heavy section gates are more expensive to galvanise than lightweight gates. Galvanising will last for years.
Other methods of preventing rust are not as robust as galvanising and could be called rust inhibitors. These include painting with a red oxide primer, painting with a galvanising paint and other metal primers. These provide some protection but will need much more maintenance.
Only hot zinc dip galvanising will guarantee a rust proof finish.
What is the difference between painting and powder coating?
Once gates have been galvanised or treated with a rust inhibitor they can be painted. Hammerite paint is the most commonly available metal paint and is a popular finish, widely available and easy to touch up.
Powder coating is carried out in a special powder coating oven. The finish is thin and smooth. Powder coating can vary in quality and contrary to popular belief does not prevent rust. It can also be prone to chipping and fading on outside products.
Another alternative is a two part epoxy paint. This is a high gloss finish, similar to that on cars.
Finishing costs can make quite a difference to the price. Always check the finish and what it actually means. A black primer is a thin coat of black metal paint. It might look OK at first but without further painting or treatment will almost certainly rust on outside products.
