No, mild steel is not a suitable material for use in a lead-lined reactor for phenol sulfonation with concentrated sulfuric acid. Phenol sulfonation is a highly exothermic reaction and mild steel is not corrosion-resistant enough to withstand the extreme temperatures and pressures generated by this reaction. It is recommended that you use a stainless steel reactor lined with lead for this application.

Redintor Bautista

It is not recommended to use mild steel reactors lined with lead for phenol sulfonation with concentrated sulfuric acid. Lead is susceptible to corrosion by strong acids, and sulfuric acid is a highly corrosive substance that can react with lead, leading to degradation of the reactor and potential release of toxic lead into the reaction mixture.

For phenol sulfonation with concentrated sulfuric acid, it is recommended to use reactors made of materials that are highly resistant to corrosion by sulfuric acid, such as stainless steel, Hastelloy, or Teflon-lined reactors. These materials provide a longer service life, improved safety, and reduced maintenance costs compared to mild steel reactors lined with lead.

Hastelloy is the best solution for this purpose. Stainless steel could be problematic if for any reason the water would be present of formed during reaction.

You may want to check my posts for a related query elsewhere at this forum:

https://www.researchgate.net/post/Oleum-corrosion-what-steel-or-nickel-alloy