A515 vs. A516 steel

[jdod]

thread330-14909
would the A516 be more prone to corrosion than the A515 if both were used to store liquids that had a pH of 3.8 - 4.1?

 

[blacksmith37]

The difference is 516 is "fine grain practice" and should have better toughness due to smaller grain size. Any difference in corrosion resistance ( if any) would be a function of the particular heat; residuals like Cu , etc. When they were written 515 was expected to have larger grain giving it a slight advantage in high temperature strength.

 

[jdod]

Thanks for the prompt response. We must have another unseen problem. We are replacing some steel containers that are 43 years old made of 515, with no corrosion or pitting evident (UT readings have been taken). We are testing some 10 year old tanks made of 516 and they are showing pitting and corrosion. Both sets of containers are in identical services.

 

[weldstan]

At one time A515 could be and was produced with fine grain melting because there was no prohibition thereto. It was subsequently revised to require coarse grain melting. As blacksmith37 stated the original intent was to produce 515 to coarse grain practice and 516 was specified to be made with fine grain melting to differentiate the two specifications when they replaced A-212.


Some of the steels made 40+ years ago had more residual tramp elements that provided greater corrosion resistance than some of the "cleaner" steels made today.

 

[EdStainless]

At that age residual chemistry is the issue, not grain size.
You need to take samples and have some good analysis done.

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P.E. Metallurgy, Plymouth Tube

 

[Guest102023]

Does the liquid contain HF acid? Residual alloy elements have been shown to offer some protection from corrosion in HF. The formula used to screen susceptible material escapes me at the moment but I can find it.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[jdod]

The only information I have quick access to is the SDS sheets, and hydroflouric acid is not listed.