ASTM A516 Gr. 70 NACE MR 0103 Plates vs Standard A516 Gr. 70 Plates
Both plates start from the same base material. ASTM A516 Gr. 70 is a carbon steel plate grade built for pressure vessels, but once a project involves H₂S exposure, the specification changes completely. Buyers sourcing ASTM A516 Gr. 70 NACE MR 0103 / MR 0175 Plates need to understand where the NACE requirement adds testing and documentation that standard plate orders never touch. Getting this wrong at the procurement stage creates rework and rejection at inspection.
What Is Standard ASTM A516 Gr. 70 Plate?
A516 Gr. 70 is a carbon steel plate grade developed for moderate and lower temperature service in pressure vessels, storage tanks, and boiler applications. It carries a minimum tensile strength of 70,000 PSI and a minimum yield strength of 38,000 PSI. Refineries and fabricators specify standard A516 Gr. 70 plates where the process fluid does not introduce hydrogen-induced cracking risk. The grade alone says nothing about sour service capability.
What Makes A516 Gr. 70 a NACE-Specified Plate?
NACE is not a separate steel grade. It is a compliance requirement layered on top of the base material whenever equipment handles sour environments containing hydrogen sulfide (H₂S). Two standards govern this: NACE MR0103, written for sour refining and process equipment, and NACE MR0175/ISO 15156, which covers oil and gas production equipment exposed to H₂S at the wellhead. A516 Gr. 70 NACE MR 0175 Plates and NACE MR0103 Plates both restrict hardness and chemical composition, but they apply to different segments of the sour-service chain. Selecting the correct standard depends on where the vessel sits within the process, not on preference.
A516 Gr. 70 NACE vs Standard A516 Gr. 70: Key Differences
Standard Gr. 70 plate ships once it meets ASTM A516 mechanical and chemical requirements. ASTM A516 Gr. 70 NACE Plates carry that baseline plus a service-specific compliance layer. The environment changes first: standard plate suits general pressure vessel duty, while NACE material targets vessels exposed to wet H₂S. Material selection tightens next, since NACE-compliant heats require controlled sulfur content to limit cracking susceptibility.
Hardness restrictions apply only on the NACE side. MR0103 and MR0175 cap surface hardness at or below 22 HRC for carbon steel, a limit standard A516 Gr. 70 has no obligation to meet. ASTM A516 Grade 70 NACE Plates require records tying each plate to its NACE compliance basis, while standard orders close out with a routine mill test certificate. HIC testing, where specified, sits exclusively on the NACE and sour-service side, never as a default addition to plain Gr. 70 material.
Does Standard A516 Gr. 70 Provide HIC Resistance?
No, standard A516 Gr. 70 specification confirms mechanical properties and chemical composition within ASTM limits. It does not test for hydrogen-induced cracking, and treating a routine mill certificate as proof of HIC resistance misrepresents what that document covers. Projects requiring HIC resistance must state the applicable testing standard, typically NACE TM0284, along with acceptance criteria for crack length, crack thickness, and crack sensitivity ratios. A516 Gr. 70 HIC Plates only qualify as HIC-tested once the plate passes these tests, and buyers should request the test report rather than assume compliance from the grade name alone.
A516 Gr. 70 NACE Plate Testing and Documentation
Each plate is shipped with a mill test certificate showing heat number, plate number and full chemical and mechanical results. Heat to plate traceability is maintained through production. Where the purchase order references NACE MR0103 or MR0175, the supplier performs hardness testing over the entire plate surface and records compliance with the referenced clause. A516 Grade 70 HIC Tested Plates additionally carry HIC test reports covering crack ratios per NACE TM0284, run on samples from the qualified heat. Impact testing follows when the design code requires it, and third-party inspection agencies witness testing before plates are released for dispatch.
Which A516 Gr. 70 Plate Should Buyers Specify?
Specify standard Gr. 70 for pressure vessels and tanks operating in dry, non-sour service. Once equipment is in sour-service scope as defined by the process safety data or design code for the project, then move to NACE MR0103 Plates or MR0175 material. Add HIC testing on top of the NACE requirement only when the specification calls for it, since HIC testing and NACE hardness compliance address related but distinct risks.
Choosing Between Standard and NACE A516 Gr. 70
The right plate depends on process conditions, not on upgrading for the sake of margin. Match the material to the applicable NACE requirement, the governing design code, and the project specification, and confirm the testing scope with the supplier before placing the order. RPF Pipes & Fittings supplies both standard and NACE-compliant A516 Gr. 70 plates with full documentation. Contact us to confirm the correct specification for your project.