Hi there,

You can check from the linnk: http://www.meadinfo.org/2015/08/s355-steel-properties.html

Hello Rifnur,

I don't know those alloys particularly. However being of different composition you should consider that the energy surface of your samples is going to differ. This factor may affect the adhesion of your organic coating on the metal substrate and thus decreasing protection. Other factor that may also vary is the presence of impurities or precipitations (e.g. chromium carbides on stainless steels) that can act as a point of varying voltage (and thus a local galvanic cell). Grain size can also differ however, this depends not only of the composition but also of the sample's thermal history. Usually grain boundary is a starting point for corrosion.

Which test you do to verify adhesion? A common example is Cross-Cut test (ASTM D3359 - 07). Have you seen a difference between the two samples?

Hello Ricardo,

Thank you for the answer. It is very informative.

There is indeed some difference in the composition, not significant though. But anyways I plan to test the adhesion by both cross cut test you have mentioned and pull off test (ASTM D4541). I have not checked it yet. If that is interesting for you I can share them with you when I will have them.

I do not possess extensive information regarding the impurities on the surface of the different panels, though they both are prepared (washed and blasted) according to ISO standards.

Grain size is an interesting point. There is difference in the grain size, and the finer grain size panels are the ones with better results. I am going to check the magnitude of the difference, if it is big enough to have an impact.

These are structural steels having yield strength of 235 and 355 MPa, respectively. These can be produced from same chemistry but different rolling schedule w.r.t. finish rolling temperature and post-cooling. Else, minor addition of microalloying in case of S355 grade steel may be done to achieve high strength.

Corrosion is a surface phenomenon and is strongly affected by surface features, whether chemistry, microstructure, surface roughness, etc. Since you are working on the coating of these steels, I don't think there will be any difference in coating of both the steels as these are not distinctly different.

the estructural steels can be manufacturated by many diferents  methods that include rolling, whatever, this process can be change the surface propiertes and then can be modified the corrosion speed.

S255 and S355 are structural steels covered by EN10025-2. They are compositionally very similar with the main differences being that the maximum carbon and manganeese concentrations are slightly higher for S355. The max. C and Mn concentration for S235 is 0,17-0,20% and 1,4%, respectively, and for S355 0,20-0,24% and 1,6%, respectively.

It is difficult to imagine that such small compositional differences should have a significant impact on corrosion and to my knowledege it is not something that is normally considered when specifying corrosion protection systems for structural steels. I think factors that can affect the performance of the coatings are far more important, e.g. surface roughness or surface profile.

Hello Rifnur,

The corrosion of the two steels is due to the chemical composition and the impurities of the way of production. In addition, the crystal structure will have a significant impact. The smaller the structure becomes more corrosive. This is due to the large amount of boundaries. Corrosion collapses faster and the material undergoes plastic deformation. This detracts from the created internal stresses between the crystalline beads.

thank you all for your answers!

Hi there,

You can check from the linnk: http://www.meadinfo.org/2015/08/s355-steel-properties.html