Dear M. Yehya ,

Good morning!

I would suggest you to have a look on "Isocorrosion Diagrams". Usually, the maximum corrosion rate should be below 0.1 mm a year, but it will depend on the project... For some cases, weld overlay and/or weld buildup are acceptable to increase the thickness of already corroded plates and sheets as a maintenance procedure from time to time. Please review ASME Section IX QW-202.3 "Weld Repair and Buildup".

Dear Dr. M. Yehya ,

I believe that the maximum limit of corrosion depth or mass loss in a metal that corrodes in a given environment essentially depends on the type of application and performance required of the material itself.

For example, the extent of localized corrosion phenomena that can be neglected in a certain use are instead critical if the same material has, for example, a structural function and must instead resist critical conditions that can generate risk conditions (e.g. mechanical stress, problems related to flows and pressures of liquids and / or gases, etc.) for the safety of man and the environment.

The subject is very sensitive and to be successful the operation requires a multidisciplinary approach in which the design engineer and the corrosion expert collaborate together.

I suggest you to have a look at the following documents:

- Predicting long-term corrosion of metal alloys in physical infrastructure

Melchers, R.E.

npj /Mater Degrad 3, 4 (2019)

Available at: https://www.nature.com/articles/s41529-018-0066-x

-ASTM G1–90 (Reapproved 1999) -Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens

Available at: https://tinyurl.com/y4gj6qef

- ISO 8044:2015(en) Corrosion of metals and alloys — Basic terms and definitions

Available at: https://www.iso.org/obp/ui/#iso:std:iso:8044:ed-4:v1:en

My best regards, Pierluigi Traverso.

During the design stage, based on the life of vessel estimation and taking the maximum corrosion rate that has been established in the worst or aggressive environment conditions, the designer will provide the corrosion allowance over the required thickness for catering pressure and other secondary loads. As long as the CA is available your equipment is safe.

Thank you all for your help!