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How to Read a Material Test Certificate (MTC)
Every order that leaves us carries a Material Test Certificate. Most buyers file it without reading it, and most of the time that is fine — until a PMC firm, an auditor or an electrical inspector asks what is actually on it.
This guide is about the document itself: what an MTC is, what each block on it means, which claims a supplier can legitimately make and which ones need a mill behind them. It is written from the supplier side, because we issue these certificates and we have had to decide, line by line, what ours is allowed to say.
One rule sits underneath all of it, and it is the rule we build ours to: a certificate never prints a number nobody measured.
First Distinction
Mill certificate or material certificate? They are not the same document
"MTC" gets used for two different papers, and confusing them is the single most common mistake at handover.
A mill test certificate is issued by the plant that made the metal. It reports what the mill’s own laboratory found on the heat it produced — chemical composition, mechanical properties — because the mill has the spectrometer and the tensile rig, and because it made the material and can trace it.
A material test certificate is issued by the supplier who supplied the consignment. It identifies the material against a specific invoice and states what that supplier genuinely verified before it left: coating readings taken with a gauge, dimensions, surface condition, net weight.
Both are useful. They answer different questions. A supplier issuing a document that reads like a mill certificate — full composition table, tensile figures, hardness numbers, all under a column headed "Observed" — is asserting tests it has no equipment to perform.
Global Electric Company is a supplier. We hold stock, we inspect it, and we ship it. We do not roll steel, we do not galvanise, and we do not operate a testing laboratory. What we issue is a material test certificate, and it is scoped to exactly that.
Anatomy
The five blocks of a real certificate
Strip away the letterhead and any competent MTC is five blocks. If one of them is missing, the document is decorative.
| Block | What it contains | What it proves |
|---|---|---|
| Identity | Date of issue, and a reference that ties the certificate to one consignment | That this paper belongs to your material and not to someone else’s |
| Consignment reference | Invoice number, invoice date, customer | The link between the certificate and the goods you actually received |
| Material description | What the material is, the standards it is supplied against, and a line-by-line list of what was in the consignment | That the certificate covers the sizes on your delivery, not a generic product |
| Test / inspection results | Each check, the method used, the observation, and the result | The substance of the document |
| Certification | A signed declaration, scoped to that consignment | Who is standing behind it, and how far |
Our certificate carries no serial number of its own. The invoice reference is its identity — one invoice, one certificate, and the same invoice always renders the same certificate. That last property is the one an auditor actually tests, and it is worth checking on any certificate you are handed: ask for the same one twice and see whether the numbers move.
It is also always one page. A material certificate that runs to four pages is usually padding a thin middle block.
The Numbers
What the figures on a GI certificate actually mean
On a galvanised steel earthing strip, the meaningful checks are about the coating. The base steel is a commodity; the zinc is what decides whether the strip survives twenty years underground.
Here is what each line on our GI certificate is reporting, in plain terms.
- Coating thickness, in microns (µm). Measured on samples drawn from the supplied lot with an Elcometer gauge — a hand-held instrument that reads the zinc layer without cutting the strip. Reported as the individual readings, plus an average derived from them.
- Uniformity of coating (Preece test) — IS 2633. Whether the deposit is continuous, or whether there are bare spots where the zinc did not take.
- Adhesion of coating — IS 2629. Whether the coating is bonded to the steel or is flaking and peeling off it.
- Visual inspection — IS 2629. Continuous, smooth coating, free from gross imperfections. The least glamorous line on the page and the one that catches the most problems.
- Base steel — IS 2062. The mild steel the flat is rolled from, stated in the material description block.
- Galvanizing — IS 2629 practice, IS 4759 coating. How the zinc was applied and what the coating has to be.
A note on the coating numbers, because it is the part people misread. Coating thickness is not uniform. It varies along a lot, and it varies with section — galvanising deposits differently on a 25×3 flat than on a 75×12. That is why a certificate should report readings, plural, from a sample, and why a single suspiciously round figure repeated across every line should make you ask where it came from.
Our readings are recorded per lot and per size, when the lot lands. A certificate prints the readings for the lot in force on its invoice date. A size with no reading on file gets no coating figure on its line — not a borrowed one from the nearest size, not an average of the others.
If you want the sizing side of this rather than the certificate side, the GI strip sizing guide covers cross-sections, weight and the galvanising allowance.
Provenance
Every number should say who measured it
This is the test that separates a real certificate from a decorative one, and you can apply it to any supplier’s document in about thirty seconds.
For each figure on the page, ask: who measured this, with what, and where is that stated?
A certificate that can answer will show you three things next to every number — the method, the observation, and the result. On ours, a coating reading carries "Elcometer gauge" as the method and says in the observation that it was measured by Global Electric Company. There is no ambiguity about whose finding it is.
Where a figure comes from someone else — a galvaniser’s or a mill’s own certificate — the honest treatment is attribution, not adoption. The figure is printed as declared, said to come from the material supplier’s mill test certificate, and marked not measured by Global Electric Company. It never reads "PASSED", because we did not test it and so we cannot pass it.
That distinction matters more than it sounds. A supplier-declared figure printed as though it were the supplier’s own finding puts a number under a letterhead and a signature that nobody at that company ever took. A customer’s QA department and an auditor both read it as your testing. Attribution gives the customer the same assurance without misleading anyone about who did what.
The Blank Row
What ours does when nobody measured
The uncomfortable case is the one that tells you most about a certificate.
If no measured lot covers the invoice date for a given size, our certificate carries no coating figure for that line at all. The row is simply absent. Not a placeholder, not a nominal range, not the nearest size’s numbers.
That looks like a gap, and it is meant to. The alternative — filling it with something plausible — is how a document stops being evidence. A certificate that has a number for everything, always, in every column, has told you nothing except that its author was unwilling to leave a space.
The same discipline decides what our copper certificate says. We do not test copper purity: that needs a spectrometer, and a supplier does not have one. So our copper certificate does not present a composition figure as our own finding. What it states is what we genuinely verify:
- Dimensions and section — width and thickness within the ordered tolerance, checked against the dimensional requirements of IS 1897:1983. That standard is cited for dimensions, and for nothing else.
- Surface and visual inspection — clean, smooth surface, free from harmful defects.
- Net quantity by weighment — the net weight tallies with the invoiced quantity.
And the certification block on the copper document is deliberately narrower than the one on the GI document. It does not claim wholesale conformity to a list of standards. It says the material was inspected as stated, that dimensions and section conform to the ordered specification, and that net quantity is verified by weighment. That is the extent of it.
Some buyers find that thinner than they expected. It is thinner. It is also the part of the document that will still be true in three years when someone re-reads it. If your specification needs assurances beyond that on copper, say so at enquiry stage and we will tell you plainly what can and cannot be evidenced — the copper vs GI guide covers where each metal belongs.
Watch For
When a certificate looks too complete
Nobody gets suspicious of a thin certificate. The risk runs the other way: the impressive ones, dense with tables, are the ones worth reading twice.
- A full chemical composition table from a trader. Composition needs a spectrometer. A stockist who is not the mill either got it from a mill certificate — in which case it should say so — or it came from somewhere else.
- Tensile strength and hardness figures, unattributed. Same test, same answer. These come off a testing machine that a supplier does not own.
- Numbers that move between copies of the same certificate. Ask for the certificate for one invoice twice, a week apart. If the readings differ, they are being generated, not recorded. This is the fastest test on this list and almost nobody runs it.
- The same figure on every line, every size, every month. Real measurements vary. A constant is a default.
- A conformity claim wider than the tests shown. If the results table checks three things and the declaration claims conformity to six standards, the declaration is doing work the tests do not support.
- "Conforms to IS 3043" as a material claim. IS 3043 is a code of practice for earthing systems — how they are designed, installed and tested. It is not a product conformity standard for a length of strip. On a certificate it belongs against the application the material is supplied for. The standards that certify the metal are the material ones: IS 2062 for the base steel, IS 2629 and IS 4759 for the galvanizing, IS 2633 for coating uniformity.
- No invoice reference. A certificate that is not tied to a consignment can be attached to any consignment.
Ask The Supplier
Six questions worth asking before you accept a certificate
- Who took this reading, and with what instrument? A supplier who measures can answer immediately.
- Is this your measurement or your supplier’s declaration? Both are acceptable. Only one of them is your supplier’s own finding.
- Does this certificate cover the sizes on my delivery challan? Line-by-line, not generically.
- What happens when you have no reading for a lot? The answer tells you everything. "We leave it blank" and "we put the standard figure" are very different companies.
- Can I have the certificate for this invoice number again next month? It should come back identical.
- Which standard is being claimed for what? A standard cited for dimensions is not a standard cited for grade.
None of these are hostile questions. Any supplier who has thought about their documentation will have ready answers, and the ones who have not will tell you something useful by struggling.
Get One
The certificate ships with the material
A Material Test Certificate goes out with every order — not on request, not for a fee, and not as a follow-up email three weeks after dispatch when the handover file is already being compiled. It references the applicable material standard for what you bought, so your client’s handover file is complete and your inspector has a document to look at. It is what PMC firms, quality inspectors and structural auditors normally ask for on large projects.
We have supplied earthing material to project sites across Karnataka since 2014, and the certificate has travelled with all of it.
To get a quote, WhatsApp us three things and you will usually get the number in one reply:
- Size & material — e.g. 50×6 mm GI strip, or 25×3 mm copper strip
- Quantity — in kg, or in metres and we’ll convert
- Delivery location — your Bengaluru site
If you are a consultant writing the clause rather than buying against it, send us the earthing clause and we will tell you which material and which certificate it calls for.
FAQ
Material Test Certificates — Common Questions
Related Guides
Related guides
- GI Earthing Strip Sizes — IS 3043 strip sizing and the full size chart.
- What Goes in an Earth Pit — the five components of an IS 3043 earth pit.
- Copper vs GI Earthing — when GI is enough, and when copper earns its premium.
Send Your Spec — Certificate Included
Every order ships with a Material Test Certificate that states what was actually verified. Send your size, quantity and delivery location for today’s rate.