Stainless Steel Corrosion Vs Ph

Nitrogen stainless steel cr23n1 2 against general and pitting corrosion in chloride environments with ph 1 12.

Stainless steel corrosion vs ph.

Without knowing further details a general statement can be made that the lower the ph is from neutral the worse the corrosion whereas ph in the basic range is apt not to be an issue. Corrosion resistance of stainless passive layer vs. Others factors are also influenced on ph. The corrosion rate of 316l ss increases with increasing ph in hydrogenated high temperature water at 300 c.

Oxy hydroxides of fe and cr 2 3 nm thick 0 002 0 003 µm transparent adherent self repairing mild steel coat. Ph for ss316 is very complex. Coatings steels passive film on stainless steel. When you compare stainless steel 17 4 ph vs 316 it is obvious that 17 4 ph has higher hardening content.

Crevice corrosion this corrosion occurs when a crevice between the stainless steel and another material. Zf for example a test indicates a corrosion rate of ool mils penetration per year for steel a and 002 for steel b it should not be concluded that steel a is twice as good as steel b but rather thati. Other considerations include ph chloride concentration and temperature of the environment in which the steel is used. The results are compared to these for conventional austenitic chromium nickel stainless steel cr18ni9 aisi 304 ss.

The phd is an index demonstrating the resistance of the passive film to breakdown and the most important alloying elements determining the phd are cr and mo. The film resistance decreases and the corrosion current density increases as the ph rises from 6 42 to 7 52 for 316l ss. So it is not possible to give a ph range that 316l stainless steel can handle. The effect of ph on the corrosion behavior of 316l stainless steel ss was investigated.

Both the grades i e. The corrosion resistance of 17 7 ph is comparable to that of type 304 stainless steel especially in the ch 900 temper and it has been used for spring applications washers eyelets fittings and fasteners. Acidic attack on stainless steels is very complex and depends not just on the ph but what acid is present whether the acid is weak or strong the type of acid non oxidizing versus oxidizing the temperature and level of dissolved oxygen. In the case of crevice corrosion of stainless steel the depassivation ph is the ph at which the anodic dissolution rate rapidly increases and depends on the alloying element.

Precipitation hardening grade is a combination of two stainless steel structures i e.