All Carbon Equipment trailers are galvanised, but we do sometimes get asked if we can supply a cheaper painted trailer, or why a customer should spend more for one of our galvanised trailers.
Painted trailers are an option we choose not to sell though because we want our trailers to be useful for years to come, and painted trailers aren’t up to the task.
Painted trailers are usually painted on the outside only using single-stage enamel spray paint, which is a fast and cheap alternative to the 2K paint that is used on cars. Not only is it more susceptible to sun damage, but it is also thinner and softer than automotive paint. It’s not uncommon to see cars which have been left outside with faded and peeling paint, and we all know how easy it is to scratch a car especially with something as hard as rock or metal.
Trailer paint is even easier to damage than that, and if we were to use an automotive-style painting process, the cost would be almost the same as galvanising. There is also no protection for the inside of the chassis, so trailers left outdoors can quickly rust from the inside out.
Hot-dip galvanising is very different to painting. Steel components, such as our heavy-duty trailer chassis, are dipped into a large vat of molten zinc. This molten zinc bonds with the steel and coats all surfaces both inside and out.
The result is a solid metal coating that is much thicker and tougher than paint. Abrasive materials like rock or sharp metal tools like shovels which can easily scratch or chip soft paint take a very long time to wear through zinc. But the biggest advantage of zinc is that if you do manage to chip or scratch away the zinc coating, the steel below is still protected because the zinc will act as a sacrificial anode.
What this means is that the zinc actually rusts or corrodes easier than the steel, so if you have a piece of zinc and steel next to each other, the zinc will rust before the steel does. The key difference though is that when zinc corrodes it goes through a number of chemical reactions to form a thin but durable zinc carbonate layer which protects the zinc from corroding further. If this layer is damaged the zinc below corrodes slightly more and reforms the protective layer. Steel, on the other hand, creates the brown rust we are all familiar with, which easily flakes away revealing more fresh steel to corrode, and undermines the surface to which any paint is applied.
There are a few disadvantages to hot-dip galvanised trailers though. Firstly, there is only one colour available which starts as a shiny silver and fades to a matte grey once the zinc carbonate layer has formed. If you need a coloured trailer to match your vehicle or company branding, the trailer has to be painted on top of the galvanising. The paint serves purely as a decorative coating though and is not used to protect the steel.
The galvanising process is also very hot, the molten zinc is held at a temperature of 450c which heats the steel components when it is dipped. As the steel expands and contracts at slightly different rates this causes some small internal stresses which will warp large sheet metal areas such as the floor of the trailers. While we work to minimize this effect unfortunately it is not feasible to have a perfectly flat galvanised floor so all our trailers do have a slightly wavy floor. For most customers, this is primarily an aesthetic issue and doesn’t cause any issues for day-to-day uses.
The final disadvantage is that welding on the trailer is slightly more difficult, and loses the advantages of galvanising at the joints when the zinc is burnt away. Some manufacturers make their chassis from galvanised steel rather than hot-dip galvanising the complete chassis like Carbon Equipment trailers. These manufacturers still advertise as a galvanised trailer, however, each of the dozens of welded joints is only protected on the outside of the trailer by paint so it’s important to look for hot-dip galvanised trailers.
After considering these factors, Carbon Equipment strongly believes that galvanised trailers are well worth the extra upfront cost, which will likely be more than paid back by the additional years of use you get from galvanised trailers. This is why all our trailers are galvanised as standard, and we choose not to offer a cheaper painted option, and why we can offer a structural warranty because we know our trailers won’t rust inside or out.