What steel grade is best for signage is rarely asked when customers enquire after stainless steel lettering or stainless steel signage, they assume: “Stainless is stainless, of course it won’t rust”….but…!
the truth is:
Stainless steel is corrosion resistant
Stainless steel is not corrosion proof
And not all stainless steel is the same
In signage, especially external signage, the grade of stainless steel you choose can make the difference between a sign that looks premium for 10+ years… and one that starts showing rust staining far sooner than expected.
This is particularly important in coastal locations like Brighton & Hove, Shoreham, Worthing, Eastbourne, Seaford and along the South Coast, where salt in the air accelerates corrosion.
Why Stainless Steel Can Rust on Signs
Stainless steel resists corrosion because it contains chromium, which forms a protective surface layer.
However, in real-world signage conditions, stainless steel is exposed to:
- Salt in the air (coastal environments)
- Road salt (winter conditions)
- Acid rain and pollution
- Cleaning chemicals
- Constant moisture and condensation
- Metal-to-metal contact (fixings and locators)
Over time, these factors can break down the protective layer, causing visible staining or corrosion.
What steel grade is best for signage?
Let’s review the different grades of steel typically used in signage.
304 Stainless Steel (Standard Stainless)
304 is the most commonly used stainless steel and is widely available.
Typical signage uses:
- Internal stainless lettering
- Feature walls and reception branding
- Covered exterior areas (with less exposure)
The issue:
In coastal or harsh outdoor environments, 304 can develop surface staining (often called tea staining) which can look like rust spots or streaks.
316 Stainless Steel (Marine Grade Stainless)
316 is often referred to as marine grade stainless steel.
It contains additional alloying elements (including molybdenum) which make it significantly more resistant to salt corrosion.
Typical signage uses:
- External stainless lettering
- Coastal shopfront signage
- Marine businesses and yacht clubs
- Fixings and locators for exposed signs
- Stainless trays and built-up letters outdoors
If your signage is installed anywhere near the sea, 316 is the best long-term choice.
430 Stainless Steel (Budget Stainless, Not Recommended for Exterior Signage)
430 stainless is sometimes used in low-cost decorative applications.
In signage, 430 is best avoided externally, because it has much lower corrosion resistance and can stain or corrode faster
What steel grade is best for signage – It’s Not Just the Letters
This is the part most people miss…
Even if your stainless letters are high quality, the fixings might not be.
In signage, stainless steel is used in:
- Built-up letters
- Flat-cut letters
- Returns and trims
- Trays and sign panels
- Stand-offs and spacers
- Locator fixings
- Studs, screws and bolts
If any part of the sign uses a lower grade, you can get corrosion staining that spreads and spoils the overall appearance.
What steel grade is best for signage, especially in coastal towns.
If your signage is installed in a coastal environment, the safest recommendation is:
316 marine grade stainless steel for all exposed metalwork
That includes:
- the letters
- the tray
- the locators
- and the fixings
What steel grade is best for signage, a good rule of thumb: If you can smell the sea air, choose 316.
What Happens If You Choose the Wrong Grade of steel for signage?
Using standard 304 stainless steel on coastal signage can lead to:
- Brown staining on letters or trays
- Rust marks around studs and fixings
- Visible streaking beneath lettering
- A sign that looks “dirty” even when it’s clean
- Premature replacement or refurbishment
And because signage is often high up, cleaning or replacing it can be far more expensive than choosing the correct grade in the first place.
Our Recommendation for what steel grade is best for signage.
When we manufacture stainless signage, we always consider:
- Location of installation
- Exposure to salt air
- Fixing method
- Sign depth and water trap
- Long-term maintenance
For coastal projects, we typically recommend 316 marine grade stainless steel, so the signage continues to look sharp and premium for years.
Need Help Choosing the Right Stainless Steel for Your Sign?
If you’re planning:
- Stainless steel letters
- A sign tray with stainless detail
- Shopfront signage
- Coastal building signage
- Marine business signage
…we’ll happily advise you on the most suitable grade for the job.
The right material choice now prevents expensive problems later.
