Chemical Analysis Certificate: Types, Required Elements & How to Verify Results

A chemical analysis certificate records the elemental composition of a material — the actual measured percentages of carbon, manganese, chromium, nickel, and other alloying elements. It is one of the two core data sets on a Mill Test Certificate (alongside mechanical test results) and is the primary tool for verifying that the correct alloy has been supplied.

Quick Answer

---

Types of Chemical Analysis Certificate

1. Mill Certificate (Ladle and Product Analysis)

The most common form. The steel mill reports:

• Ladle analysis — sampled from the molten heat before casting; this is the primary chemistry record
• Product analysis — sampled from the finished product (plate, pipe, bar) after rolling; may differ slightly from ladle analysis due to segregation

Both analyses are reported on the same EN 10204 3.1 or 3.2 certificate. When they differ, the product analysis is the governing value for specification compliance.

2. Independent Laboratory Certificate

An accredited laboratory (ISO 17025-certified) performs its own analysis on a sample cut from the delivered material. This is used to:

• Verify the mill's own certificate independently (required for 3.2 documents)
• Re-certify material where the original certificate is lost or suspect
• Provide legally defensible evidence in a dispute or failure investigation

Laboratory certificates must reference the laboratory's accreditation number, the method used (ASTM E1086 for OES, ASTM E1473 for ICP-OES), and calibration traceability.

3. PMI (Positive Material Identification) Report

A PMI report records field measurements obtained by XRF or arc/spark OES on installed or incoming material. PMI is used for identification and verification — it is not typically used as the primary certification of chemistry for a new heat of material.

See detailed guide: Positive Material Identification (PMI)

---

Key Elements Reported by Alloy Family

Carbon and Low-Alloy Steels (e.g., ASTM A516, A106, A333)

Stainless Steels (e.g., ASTM A312 TP316L, A276)

In addition to the above, report: Cr (corrosion resistance), Ni (austenite stability), Mo (pitting resistance), N (strength in austenitic grades), Ti/Nb (stabilized grades), and Pb (restricted in nuclear grades).

Important: For L-grades (304L, 316L), verify C ≤ 0.030%. This is critical — supplying standard-grade (C ≤ 0.080%) material labeled as L-grade is a serious non-conformance.

Duplex and Super-Duplex Stainless (e.g., UNS S31803, S32750)

Report Cr, Ni, Mo, N, W (for super duplex), and calculate the Pitting Resistance Equivalent Number (PREN = Cr + 3.3Mo + 16N). Minimum PREN thresholds are specified per application.

Nickel Alloys (e.g., Alloy 625, Alloy 825, Alloy C-276)

Ni, Cr, Mo, Fe, Nb, Co, Ta — multiple elements must be within narrow bands. Also verify that the "not more than" limits for trace elements are met.

---

How to Verify Chemical Analysis Against the Specification

1. Identify the governing specification — from the purchase order (e.g., ASTM A516 Grade 70)
2. Locate the chemical requirements table — in the ASTM standard, typically Table 1 or Table X
3. Compare each reported element against the min/max limits — not just carbon; all reported elements
4. Check derived values — Carbon Equivalent (CE), PREN, or equivalent carbon for weldability assessment
5. Verify the certificate states ladle analysis, product analysis, or both
6. Confirm that the heat number on the certificate matches the material — this step is frequently skipped and is the root cause of many material mix-ups

---

Analytical Methods

Optical Emission Spectrometry (OES)

• Technique: Arc or spark excitation of a polished metal surface; emitted light analyzed by spectrometer
• Accuracy: Excellent; suitable for certification purposes
• Coverage: Full elemental suite for most alloy systems
• Used in: Laboratory certification, mill analysis

X-Ray Fluorescence (XRF)

• Technique: X-ray beam excites characteristic fluorescent X-rays from the sample surface
• Accuracy: Good for most elements; limited sensitivity for light elements (C, N, B below atomic number ~14)
• Portable: Handheld XRF instruments widely used for field PMI
• Limitation: Cannot reliably measure carbon content — a critical limitation for carbon steel grade differentiation

Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES)

• Technique: Sample dissolved in acid; elemental analysis in solution phase
• Accuracy: Very high; used for trace element quantification
• Coverage: Full suite including light elements
• Used in: Reference laboratory work, dispute resolution, nuclear-grade material certification

---

Common Discrepancies and Red Flags

• L-grade certificate shows C > 0.030% — material is standard grade, not L-grade
• Sulfur value missing — critical for sour service qualification; must be demanded
• Only ladle analysis reported, no product analysis — acceptable for some specifications but not all
• Heat number not matching physical marking — the number one cause of material mix-up
• "Conforms to" statement without individual element values — this is a CoC, not a chemical analysis certificate

---