Surface treatments influence on S355J2 steel

S355J2 steel‘ chemical composition of this steel can be found in Table 1. The microstructure was observed by the light metallographic microscope. All the samples were prepared by standard metallographic methods. 3% Nital was used as an etchant for visualization of the S355J2 steel microstructure.

Table1:S355J2 steel‘ chemical composition:

Figure 1 shows the microstructure of tested S355J2 steel. The microstructure revealed ferrite-pearlite matrix with a low pearlite content (local pearlite occurrence) and with average grain size of 10 μm.

 
Figure 1. Microstructure of etched S355J2 steel.

There are many step for The microstructure tested of S355J2 steel.this is the two picture tested of  S355J2 steel chosed for your reference:

The present work describes the influence of various surface treatments on morphological and corrosion properties of manganese phosphate on S355J2 steel. The most relevant conclusion is as follows:
Using the manganese phosphating process created a continuous coating on the steel surface after both mechanical surface pretreatment techniques. However, the higher uniformity of the coating and crystal size together with lower porosity and defect occurrence was obtained on ground surfaces;
Sandblasting caused increased surface roughness of the substrate compared to a ground surface. This influence was reduced after subsequent manganese phosphate formation;
Sandblasting had a negative effect on the corrosion resistance of S355J2 steel compared to ground surfaces. Worsening was observed of the relevant electrochemical corrosion characteristics including Ecorr, icorr, rcorr, and Rp after sandblasting;
The phosphate treatment reduces the corrosion rate as ascertained both in polarization curves and impedance tests by about the same extent on ground and sandblasted samples;
Manganese phosphating results in an increase of the polarization resistance of the S355J2 steel surface by more than 30 times

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