Choosing a coating thickness gauge seems complicated, but it all comes down to one simple question:
What metal is under the paint?
Picking the wrong gauge won’t just give you a slightly off reading—it will give you a completely wrong one. Here’s the simple breakdown to make sure you get it right the first time.
What’s the Difference? Ferrous (F) vs. Non-Ferrous (N)
It’s all about magnetism.
- Ferrous (F) Metals: These are magnetic. Think steel and iron. An “F” gauge uses magnetic induction to measure the coating.
- Non-Ferrous (N) Metals: These are non-magnetic. Think aluminum, copper, brass, and zinc. An “N” gauge uses an “eddy current” principle.
A gauge designed for steel (F) simply cannot get an accurate reading on aluminum (N), and vice-versa.
How to Choose Your Coating Thickness Gauge
It’s a simple 3-step process:
- Identify Your Substrate (Base Metal): What are you measuring on?
- Use a Magnet: If you’re not sure, grab a simple refrigerator magnet.
- If the magnet sticks, you have a Ferrous (F) substrate.
- If the magnet does not stick, you have a Non-Ferrous (N) substrate.
- Pick Your Gauge:
- If you only measure on steel, buy an F gauge.
- If you only measure on aluminum or copper, buy an N gauge.
What if I measure both? (The “FN” Gauge)
What if you work in an auto body shop that services both old steel-frame cars and new aluminum-body trucks? Or you’re a powder coater who gets all kinds of jobs?
You need an FN gauge (or “Combo” gauge).
This is the most popular type of coating thickness gauge. It has both sensors (F and N) built into one unit. It automatically detects what kind of metal it’s on and uses the right technology to get a reliable reading, every time.
The Bottom Line
- F Gauge = For Magnetic metals (Steel, Iron)
- N Gauge = For Non-Magnetic metals (Aluminum, Copper)
- FN Gauge = For both. It auto-detects and is the safest, most versatile choice.
Don’t guess in your quality control. Instromart can help you select the exact coating thickness gauge for your job.
Ready to get an accurate reading? Browse our full range of Coating Thickness Gauges or contact our technical team for a free consultation.
