The best paint for treating Rust

The best paint for treating Rust

What is the best paint for rust, or the best paint for treating rust?



 This is a common question, akin to, “I have a rust on my “xxxx” what’s the best paint”?
As with all painting, preparation is the key, pardon the pun. Look on most paint tech data sheets suggest “shot blast to SA 2.5”, or “mechanically abrade the surface”. This is recommended as it is ideal for removing rust, clearing the surface of any contaminants and providing a “keyed” surface or rough surface for the paint to be applied onto.

If shot blasting is not an option due to location, material, cost etc; mechanical abrasion using an angle grinder or similar is a good second option as this will have a similar, if not quite as thorough preparation of the surface. Now if like most “DIYER’s” you may have limited resources; a wire brush, a tin of paint and a brush in many cases. This is not the end of the world, there are products that will tackle corrosion in a different way, we will discuss this a little later. Let’s take the process from start to finish.

Your item has been shot blasted or you have mechanically abraded the surface, removing contaminants and providing a keyed surface. The best anti-corrosive option is to have it galvanised. This is a process conducted by professionals where the item once shot-blasted and meticulously cleaned is then immersed into high temperature liquid zinc. Zinc being the operative word and will be mentioned a few times in this blog. Galvanising is not cheap and not always an option of your item is larger than the galvanising tank or already installed into a location.

A very popular option is what is known as Cold galvanising, what is cold galvanising? This is a paint with high levels of zinc incorporated into the coating. The higher the level of zinc, the higher the rust inhibiting power. Zinc however is a relatively soft material and so can damage easier than most paints. A balance needs to be considered, more paint less protection, more zinc less durability. Zinga has 96% zinc, Galvafroid has approx. 92% and 927 has approx. 97% zinc. All of these coating can be a finish coat but ideally for added protection and cosmetic enhancement they can be overcoated with an array of primers, primer-finishes and top-coats.

If you item is heavily “pitted” with corrosion, the rust is not only on the surface but has also migrated down into the metal, an angle grinder or wire brush will not always penetrate down deep enough to remove the remnants of rust. How do you kill rust? What are the best rust neutralisers? The best for killing rust? 

At Avenue we have two options, navy steel and Ferrozinc are both water-based treatments that are applied and change colour from white to brownish-blue when they have neutralised the rust. The items can then be overcoated with a zinc incorporated primer like avenue zinc phosphate or a primer finish like zinfos340 which is a zinc phosphate incorporated primer, tint-able to any colour.

How long with will the rust stay away from a coated item? There are many factors that determine the longevity of paint, some actions are out of hands. If the substrate has been shot blasted, then galvanised and then painted or even powder-coated, 25 years is not an uncommon warranty. As with all warranties, check out the small print…… “check the item every six months, repair any localised damage or areas showing signs of corrosion….etc”. Something like an oil rig that is conducting its life in the harshest environment needs to last until its first maintenance period.

 Shot-blasting, galvanising of some but not all parts (size constraints) followed by a number of high build (thick/heavy) coatings of various two pack epoxy, zinc incorporated primers are used, followed by a number of two-pack U.V. resistant top coats. It is the preparation and then the dry film thickness of zinc incorporated paint that offers protection against the elements. Any damage to the surface will be minimised but once the surface is damaged, moisture can penetrate under the layer of paint and cause some issues. If the damage is down to the metal, corrosion will eventually be evident.

The difference between some garden furniture and an oil rig is a world apart. What is the best ant-corrosive option for garden furniture? Shot-blast, galvanising, two-pack epoxy followed by a two-pack polyurethane! In the real world there are lots of variations on a theme. Protection will come from a clean, rust-free surface, a zinc incorporated coating and film build.

1. A wire brush to remove the surface rust, a wash down to remove grease and grime. This can then be followed by spot priming any rusted areas with navy steel, a coat of avenue zinc phosphate and the various top-coat options for colour and sheen.
2. A wire brush to remove the surface rust, a wash down to remove grease and grime. Prime with a cold-galvanising paint, Zinga, Galvafroid or 927 and then prime and/or topcoat.
3. Wire brush to remove surface rust, a wash down to remove grease and grime. A or a number of coatings of a zinc-based primer finish (coloured protection primer).

Seems like a lot of effort, isn’t there a one-coat product that kills rust and gives a finish coat? The answer is no! There are products available, indicating “direct to rust”, “one-coat and forget” etc, all these products achieve is to cover the rust for a period of time, but unless removed or neutralised it is only a matter of time before it returns. The more effort you invest (time, effort, money), the longer it will last.