The prolonged exposure to damp and to atmospheric agents causes the corrosion of objects made with ferrous or alloys containing ferrous, such as steel. The corrosion of the iron is an electrochemical reaction, catalyzed by water and accelerated by acids and salts. During this reaction, the iron combines together with oxygen affording iron oxides, such as ferric oxide Fe2O3, that is a dark- reddish substance, commonly known as rust. The rust layer is permeable to air and water, this means that, if not prompt action is undertaken, the metal, below the layer of rust, keeps on corroding itself till it will be completely consumed. In fact, the layer of rust is weakly bonded to the metal from which it is generated, and after crumbling, it can expose the underlying metal to a further corrosive process.
Salts and chlorine ions can accelerate the corrosive process, this occurs when the metal is exposed to marine aerosols, acid rains, industrial or urban zones characterized by a high level of atmospheric pollution, due to carbon and sulphur oxides. In this last case, it can be observed the formation of iron hydroxides which, compared to iron oxides, can be easier detached from the surfaces from which they are generated, exposing the metal to a further corrosion.
Rust can provoke serious economic damages and it can put at risk the safety of people and things. The oxidation of the iron not only provokes the structural weakness of the metal itself, but it also causes a significant increasing of the volume of the metallic artifact. This volume expansion generates enormous forces and pressures that can break structures, such as reinforced concrete.
Some procedures in order to prevent the development of rust on ferrous artifacts, actually employed such as galvanizing, paintings, cathodic protection techniques or use of stainless alloys. On the other hand, where rust is already formed, the only possible interventions are sandblasting, sandpapering, or the application of a rust converter.
The sandblasting technique is not easy to perform and in most of the cases it implies the mechanical removal of a significant quantity of material from the ferrous artifact. Its aim is to show the shiny metal. The sandpapering technique is laborious and it, generally removes rust only partially.
This implies that the artifacts must be over-painted on a support partially rusted, which causes adhesion problems of paintings and of its finally detachment.
The use of rust converters allows, on the other side, the conversion of rust into a solid layer, which is strongly anchored to the metal and at the same time, it is a perfect promoter of adhesion for the next paintings.
Rustblock® products are the most efficient solutions in order to satisfy every operative need. In order to suggest to our clients the most suitable Rustblock®, according to its application, it may be useful to refer to the table shown below, which is a guideline for a rapid consultation.
For deeper insights, please consult the Technical Data Sheet of the products.