Stainless Steel 304 vs 316 for Sign Letters

The Short Answer

We build sign letters in stainless steel 304 or 316, and the grade is chosen per job rather than defaulted. 304 covers ordinary inland exposure. 316 is the grade to ask for where there is salt or chemical load in the air.

Both grades cut, weld, brush and polish the same way, so the decision changes the price and the service life — not the look of the finished letter.

What Actually Separates Them

316 contains molybdenum, which is what makes it resist chloride pitting. Chloride is the mechanism behind most of the rust spots you see on coastal signage, and it is why an otherwise sound 304 letter can start speckling within a couple of seasons near the sea.

Pitting is not a coating failure that can be cleaned off. Once it starts, the only real fix is replacing the character — which is why the grade decision belongs at the quotation stage.

One Question That Settles It

• How far is the sign from salt water, and what else is in the air?
• Within a few kilometres of the coast, on a harbour front, on an exposed elevation that gets wind-driven spray, or anywhere near a pool hall or a chemical process — specify 316.
• Inland, sheltered, or indoors — 304 does the job and costs less.
• If the site is marginal, the cost difference across a single letter set is usually far smaller than the cost of sending a crew back.

What Does Not Change With the Grade

• Thickness still starts at 6 mm and letter height still starts at 40 mm in either grade.
• Both take a brushed grain or a full mirror polish.
• Both can be lacquered to a RAL or Pantone reference if the bare metal is not the brand colour.
• Both ship the same way: individually wrapped, packed flat, with a 1:1 mounting template.

Specifying It on the Order

Write the grade on the artwork, not in an email. We put it on the approval drawing so it is confirmed in writing before anything is cut.

If you are not sure, tell us the site address and the elevation. That is usually enough for us to recommend one.