Rust is something we all recognise visually, but in the metal industry it becomes a serious problem: it reduces component quality, increases scrap rates and drives up production costs.
But what is rust, why does it form, which factors accelerate it and how can this phenomenon be reduced during heat treatments and hot-working processes? Let’s take a closer look.
What Is Rust?
The term rust refers to the surface layer of hydrated ferric oxides and basic iron(III) carbonates that forms on metals containing iron when they are exposed to humid air and water.
It is the result of an oxidation process:
- iron reacts with oxygen and moisture,
- loose reddish-brown compounds are formed,
- the layer does not adhere firmly to the metal and tends to flake off.
This characteristic is important: unlike other metals, such as aluminium or chromium, which form a compact and protective oxide film, rust is porous and brittle and therefore does not protect the underlying material.
Rust, Oxidation and Corrosion: The Differences in Brief
The terms oxidation, corrosion and rust are often used interchangeably, but they do not mean exactly the same thing:
- Oxidation: a chemical reaction in which a material, such as iron, loses electrons.
- Corrosion: the deterioration of a metal caused by chemical or electrochemical reactions with its surrounding environment.
- Rust: the specific product of the corrosion of iron and carbon steels, consisting of reddish-brown iron oxides and hydroxides.
In practice, rust is a specific type of corrosion that affects ferrous metals.
Why Rust Is a Problem in the Metal Industry
In industrial environments and the steel industry, rust formation is not merely an aesthetic problem. It can cause:
- Material loss: flaking oxides remove part of the underlying metal.
- Structural weakening: the component becomes less resistant and more brittle over time.
- Surface defects: oxide scales, cavities and porosity on the component’s surface.
- Increased scrap rates: components that no longer meet the required tolerances.
- Additional finishing operations: sandblasting, grinding and mechanical reworking.
For companies involved in metal forging, rolling, hot extrusion or heat treatments, rust and oxidation more generally represent a direct cost: more time, more energy and more reworking.
Under these hot-working conditions, the following may occur:
- intense formation of surface oxides,
- decarburization in steels, meaning the loss of carbon from the surface layers,
- surface defects that require the subsequent removal of material.
In addition to the “traditional” rust seen at room temperature, it is therefore essential to reduce oxidation and decarburisation during thermal processes in order to preserve dimensions, mechanical properties and surface quality.
Factors That Accelerate Rust Formation
Rust forms more quickly when certain factors are present:
- High humidity or contact with water, including rain, condensation, marine environments and salt spray.
- The presence of oxygen and pollutants such as sulphur dioxide or carbon dioxide, which accelerate the reactions.
- Rough or damaged surfaces, which expose a larger surface area to the air.
- Mechanical stress and vibrations, which can promote microcracking.
- High temperatures during hot metalworking processes or heat treatments: under these conditions, the issue is not only “rust” in the strict sense, but more generally intense oxidation and the formation of oxide scale.
In industrial processes, these factors are often present simultaneously: high temperatures, atmospheres containing reactive gases and prolonged holding times inside furnaces. It is therefore essential to implement protection strategies from the most critical stages of the process.
Oxy-Shield Protective Ceramic Coatings: What They Are
This is where Oxy-Shield protective coatings come into play. Developed by ATP, they provide an advanced ceramic coating solution for metals.
Oxy-Shield coatings are:
- protective ceramic coatings for metals,
- water-based, making them practical to handle and apply,
- designed to provide advanced control of oxidation and decarburisation during heat treatments.
Thanks to their formulation, they do more than simply protect the surface. They act more deeply on the process, providing a range of tangible benefits for companies operating in the metallurgical sector.
How They Protect Metals: A Barrier Against Oxidation and Gases
The feature that makes Oxy-Shield particularly valuable to industry is its ability to:
- delay the formation of oxide scale,
- reduce surface-related scrap,
- limit the loss of valuable metal,
- minimise secondary finishing operations,
- improve the quality of the finished product.
In other words, the ceramic coating creates a physical barrier that:
- blocks oxygen and other reactive gases,
- prevents or reduces the diffusion of harmful gases into the metal,
- helps to preserve the component’s mechanical and aesthetic properties, even after demanding thermal cycles.
Which Metals Can Oxy-Shield Coatings Be Used On?
Oxy-Shield coatings are designed to be versatile. By modifying their chemical composition, they can be applied to a wide range of metals, including:
- titanium alloys,
- stainless steels,
- tool steels,
- nickel alloys,
- carbon alloys,
- light alloys,
- zirconium alloys,
- molybdenum.
This makes them suitable for use across a variety of industries, from forging and foundries to the aerospace industry and the most complex heat-treatment processes. The objective is to provide protection from the earliest stages, helping to prevent or reduce damage caused by oxidation and decarburisation throughout the thermal cycle.
Application Methods: Flexibility for Different Geometries
Another strength of Oxy-Shield is its flexibility in terms of application methods, allowing the coating to be adapted to specific process requirements and component geometries:
- brush application – ideal for targeted applications or components with complex geometries,
- dip coating – effective for protecting large surfaces uniformly,
- spray application – a versatile solution for high-speed production and large surfaces,
- flow coating – designed for industrial-scale processes requiring even distribution across the entire surface.
This range of application methods makes it possible to integrate Oxy-Shield into different plants without disrupting existing production processes.
How to Choose the Right Protective Coating
The choice of protective coating should not be left to chance, as it depends on several parameters, including:
- type of metal or alloy, such as steel, stainless steel, titanium or nickel,
- the treatment’s temperature range,
- the process environment, including the atmosphere and the presence of specific gases,
- component geometry and handling methods,
- cycle times and plant type.
Controlling Rust to Improve Quality and Reduce Costs
Rust and, more generally, metal oxidation are not simply aesthetic issues: they represent a genuine risk to component quality, safety and the profitability of industrial processes. Understanding how rust forms and why the process accelerates in the presence of high temperatures, humidity and reactive gases is the first step. The second is to adopt specific solutions to reduce these phenomena during heat treatments and hot-working processes.
The Oxy-Shield protective ceramic coatings offered by ATP-Europe provide a targeted solution by controlling oxidation and decarburisation, improving process yields and reducing oxides, defects and secondary processing operations.
As water-based products with a customisable formulation, Oxy-Shield coatings are designed to suit a variety of industrial applications. To identify the most appropriate solution, contact ATP Europe: our technical specialists will help you select the right product for your requirements.