How to check the corrosion resistance of a cylinder liner?
High-sulphur diesel fuels are the main culprit of corrosion
Cylinder liner corrosion resistance for better product quality
Despite the progress in the automotive industry and the implementation by manufacturers of more and more electric cars on the market, we still rely on vehicles based on internal combustion engines. The operation of the internal combustion engine consists in the use by their manufacturers of the mechanism of compression and expansion of a specific fuel. Everything to create force and torque. In the construction of an internal combustion engine, the cylinder liner in which the piston moves is of great importance. It is an element of the engine block system. The corrosion resistance of the cylinder liner significantly affects the condition of our car.
Cylinder liners manufacturers prefer different. We distinguish the so-called sleeves. wet, in which the outer part is pressed into the cylinder, which remains immersed in the cooling liquid. Such bushings no longer need to be machined after being inserted into the hull, but they do have one downside. Due to the leakage between the entire circumference of the cylinder liner and the head, they cannot be used in low-valve engines.
In addition to cylinder liners, we also distinguish cast in the hull itself, i.e. from the same material, and dry ones. Dry ones are characterized by the fact that manufacturers press them into the cylinder. Such sleeves therefore do not come into direct contact with the water solution cooling the engine. The hull itself is also made of a different material. Regardless of which bush we are dealing with in our car, it should be borne in mind that it is susceptible to corrosion. So how do you check the corrosion resistance of a cylinder liner? Some piston manufacturers have already developed a way to ensure the durability of cylinder liner materials. This will make the product more resistant to the corrosion process.
The low corrosion resistance of the cylinder liner is responsible for the high emission rate of harmful gases into engine exhaust gases, the so-called EGR and the use of high sulfur diesel fuels. These factors are quite a challenge for the iron coating that covers the cylinder. Liner manufacturers have come to the conclusion over time that it is worth taking appropriate steps to change the production process of cylinder liners. First of all, it is about developing a new process for testing the resistance to rust formation. Manufacturers do this through direct actions to lead to a fair comparison of different materials and coating methods for cylinder liners. The new research method is supposed to make it possible to finally obtain a material that will be the most resistant to corrosion. This will allow the use of even stronger components over time, from which it will be possible to produce solid cylinder liners.
On the market of cylinder liners manufacturers, there are already brands that are involved in recreating the corrosive solutions of combustion products that are formed in the engine. Such solutions include, among others: nitric, acetic and sulfuric acids. Prepared boiling reactions are then used by specialists to conduct, among others, immersion tests. They allow you to reliably reproduce the properties of typical sulfur condensate and EGR.
The same experiment also uses electrochemical tests at temperatures close to the ignition temperature of the solution and metallographic inspection. On the basis of the latter test, it is possible to prove the structural condition of the material, as well as the quality of the welded joint and the reliability of the cylinder sleeve. The corrosion resistance of cylinder liners can be assessed on the basis of the tests described above. They showed that the most destructive substance for cylinder liners surfaces is sulfur. The quality of the cylinder liner, on the other hand, is significantly improved when the material from which the cylinder liners are made contains a large amount of chromium. The condition of the material is worsened by the admixture of oxides: chromium and iron.