Understanding Galvanising2020-05-07T09:56:58+10:00

Understanding Galvanising

The term “Galvanised” means a lot of things to many people so we thought we would share some basic things about galvanising, its purpose, and how to look after it.

What is it:

Galvanising is a coating applied to steel to protect it from corrosion. Sound simple… well it is, and it isn’t.
Its is a coating of “Softer” metals that is designed to slowly corrode instead of the structural steel that your trailer is made from. It is applied at specialist galvanising plants using a “Plating process” and the primary ingredient in your galvanised coating is Zinc.

Appearance: Galvanising, unlike painting or other types of coatings can produce a finish that is quite varied, based on many factors from the time in the bath, the temperature used to plate the zinc onto the steel, the flushing process etc. Also, the “Mixture” of the materials can make a difference as well. Perception is that a bright shiny finish is superior to a dull finish, however that is more a perception than anything else. A shiny finish does not necessarily mean better protection than a dull finish. Our “recipe” calls for a balance between a visually appealing relatively bright finish, and a solid coating so you get adequate protection for your frame.

Corrosion: Galvanic corrosion is a reality for anyone involved in boating, it’s a simple thing to understand, but not always a simple thing to avoid…Put simply it’s a type of corrosion that occurs when two “dis-similar” metals come into contact in the presence of a conductor. What happens is that electrical energy travels though the metals and either one of the other corrodes depending on where it sits on the “Galvanic Scale of Noble Metals” … Okay sounds confusing well it’s not.

Example: Your outboard motor has what’s called a Sacrificial Anode, this is something that has been installed by the manufacturer to prevent galvanic corrosion destroying things. Energy that travels through the different metals of the motor needs to go somewhere, so it will travel into the water that acts as the earth. When these energy particles leave the metal, they take a tiny amount of that metal with them. Think of it like an ice cube melting and you will get the picture. The Sacrificial Anode is designed to be the softest (on the galvanic scale that is) metal in your engine so all the energy that is looking to find its way to an earth travels through it and takes a little bit with it when it does. The anode is far cheaper to replace than your engine, and in most cases is replaced annually on a trailer boat.

Great: Now let’s look at your trailer… The Galvanised plating that covers your entire trailer is in fact the “Sacrificial Anode” that is protecting your steel frame.  As the trailer is exposed to moisture, either atmospheric, rain or salt water the zinc plating very slowly dissolves. This process happens from the moment the frame leaves the galvanising plant and will continue until the coating is eroded and the steel begins to corrode instead. Depending on the individual conditions this could be a short period, or it could be a lifetime.

How do I get the most out of my trailer:  Corrosion will occur at different rates depending on the environment your trailer lives in. A trailer used in fresh water, washed regularly and stored undercover could last many years and show no signs of ageing. A trailer used in salt water, unwashed and stored outdoors will not last as long. So below are our tips for maintaining the finish on your trailer and maximising its life on the road.

Keep it clean: your trailer should be washed in warm and soapy water, just like your boat, after each use. Ensure you rinse the entire trailer thoroughly taking time to flush out the inside of the chassis rails as well. Make sure you let the trailer dry thoroughly before storing and ideally store it in a well-ventilated area in the shade.

Seal any chips/scratches: the galvanised finish can be damaged and expose the steel frame beneath. As you drive gravel and debris may hit the frame and create an opportunity for corrosion to set in. Inspecting and touching up the coating with a readily available corrosion prevention paint is recommended.

It’s not a beauty contest: As the galvanised finish erodes over time the colours may change, this is a normal part of the process as you will have different thicknesses in different areas depending on their exposure. (It means that the coating is doing its job)

Replace rusty components: Rust accelerates rust so regularly inspect your trailer at the ramp when you have launched and take note of any corrosion. Prevention is by far the best cure so get in early and clean the area and re-spray, replace etc. 

DON’T: use an Acid Cleaner or any harsh chemical solvents as this will simply accelerate the rate that the galvanised finish will ablate leaving you less protection. Acid washes and Anti foul cause high levels of damage and should not be used.


Why Can’t I get my frame re-galvanised?: most industrial galvanising plants will not allow boat trailers to be re-coated as the risk of contamination of the bath is extremely high.

Expectations: Your Dunbier trailer has been manufactured to our high standards and like many owners before you we expect you will be satisfied. Look after the trailer and it will continue to look after you for many years to come.

As always please contact our customer service team if you have any questions.