Wedge Anchor Material & Finish Selection Guide

Wedge anchor finish selection is one of the most consequential decisions in concrete anchoring. The right finish for the environment delivers decades of service life; the wrong finish corrodes within months in the wrong conditions and the anchor fails. This guide walks through the four finish options available on the Simpson Strong-Tie Strong-Bolt 2 (and most code-listed wedge anchor product lines), explains when each is appropriate, and provides an application-by-environment decision matrix so you can match the finish to the job.

In This Guide:

• Pick Your Environment, Pick Your Finish
• Carbon Steel Zinc Plated
• Mechanically Galvanized (MG)
• Type 304 Stainless Steel (4SS)
• Type 316 Stainless Steel (6SS)
• Side-by-Side Comparison
• Application Matrix — Pick by Use
• How Finish Affects Load Capacity
• Code-Compliance Note for Short Variants
• Frequently Asked Questions

Pick Your Environment, Pick Your Finish

The fastest path to the right finish: identify your installation environment, pick the recommended finish below, then verify with the comparison table further down.

Environment	Recommended Finish	SKU Suffix
Interior, dry, climate-controlled — offices, warehouses, conditioned shops	Carbon Steel Zinc Plated	(no suffix)
Exterior, dry-to-moderate exposure — outdoor structural, exterior handrails inland	Mechanically Galvanized (MG)	MG
Coastal exterior, washdown, food processing — within ~5 miles of saltwater, dairy, beverage facilities	Type 304 Stainless Steel	4SS
Marine, splash zone, chloride-heavy chemical — piers, pool decks, wastewater treatment, refineries near saltwater	Type 316 Stainless Steel	6SS

Carbon Steel Zinc Plated — The Default for Interior

Zinc-plated carbon steel is the most economical wedge anchor finish and the default choice for the vast majority of interior installations. The thin zinc coating (typically 0.0002" applied via electroplating) provides moderate corrosion protection adequate for dry, climate-controlled environments. The base material is standard carbon steel, which gives the highest published load values of any STB2 finish at the larger diameters.

Best for:

• Interior structural and equipment installations
• Dry exterior applications with limited weather exposure (covered loading docks, etc.)
• General industrial and shop environments
• Code-required installations in dry interior conditions
• Cost-sensitive projects where stainless premium isn't justified

Avoid in:

• Coastal or saltwater exposure (corrodes rapidly)
• Pool decks and washdown environments
• Chemical processing facilities
• Persistently wet or condensing environments
• Long-term outdoor exposure where appearance matters

Service life: 10-25+ years interior; 1-5 years exterior depending on exposure. The zinc coating sacrifices itself before the underlying steel corrodes, so early visible surface oxidation is expected and acceptable in non-cosmetic applications.

Mechanically Galvanized (MG) — Cost-Effective Exterior

Mechanically galvanized wedge anchors carry a much heavier zinc coating than electroplated versions, applied via cold tumbling rather than heat-dipping or electroplating. The result is corrosion protection approaching hot-dip galvanized levels but with no dimensional concerns (the heavier coating doesn't fill threads or interfere with fit-up). The Simpson Strong-Bolt 2 MG is tested in uncracked concrete per AC193 and uncracked masonry per AC01.

Best for:

• Exterior structural connections in inland or moderate-exposure environments
• Outdoor handrails, equipment pads, exterior building anchors away from saltwater
• Applications where corrosion resistance better than zinc is needed but stainless cost isn’t justified
• Industrial and agricultural exterior installs
• Cold-climate exterior where freeze-thaw cycles concentrate moisture at fastener locations

Avoid in:

• Continuous saltwater immersion or splash zones (use 316 stainless)
• High-chloride coastal exposure (use 316)
• Strong acid or chemical processing exposure

Service life: 25-50+ years exterior under normal weather exposure; not rated for direct chloride immersion. The thick zinc coating sacrifices itself slowly, providing decades of protection in inland exterior conditions.

Type 304 Stainless Steel (4SS) — General-Purpose Stainless

Type 304 (also called 18-8) is the workhorse austenitic stainless steel used across most food, beverage, dairy, architectural, and general outdoor applications. Composition is roughly 18% chromium and 8% nickel, providing excellent corrosion resistance in most environments without the cost premium of 316. The Simpson Strong-Bolt 2 in 304 carbon stainless retains code-listing under ESR-3037 with full cracked-concrete qualification.

Best for:

• Coastal exterior installs (within ~5 miles of saltwater, but not in direct splash zone)
• Food processing, dairy, beverage, brewery, winery facilities
• Pharmaceutical and clean-room environments (general)
• Architectural exterior where appearance matters long-term
• Pool building structural elements (deck mounting, ladder anchors NOT in direct splash)
• General outdoor applications where appearance and corrosion resistance both matter

Avoid in:

• Direct saltwater immersion or persistent splash zones (use 316)
• High-chloride chemical processing (HCl, brine, swimming pool chemistry — use 316)
• Industrial exposure to strong reducing acids

Service life: 50+ years in most outdoor and washdown environments. 304 will eventually pit in chloride-heavy exposure; for those environments step up to 316.

Load capacity note: 304 stainless wedge anchors carry slightly LOWER tension values than carbon steel of the same diameter (due to lower yield strength of stainless alloys), but slightly HIGHER shear values at smaller diameters. See the Pull-Out Strength & Load Tables for the per-size comparison.

Type 316 Stainless Steel (6SS) — Maximum Corrosion Resistance

Type 316 stainless adds 2-3% molybdenum to the 304 chromium-nickel base, dramatically improving chloride resistance. This is the only finish suitable for direct saltwater exposure, chloride-heavy chemical environments, and continuous immersion. It carries the highest material cost in the STB2 family but is genuinely the only choice for marine and chloride applications.

Best for:

• Marine applications — piers, docks, splash zones, boatyards, boat lifts
• Pool decks and pool equipment in direct splash or immersion zones
• Chemical processing with chloride exposure (HCl, brine, hypochlorite systems)
• Industrial coastal facilities — refineries, tank farms within saltwater range
• Wastewater treatment facilities (chlorine, sewage chemistry)
• De-icing salt exposure on bridges, parking structures, transportation infrastructure
• Anywhere that 304 wouldn’t survive long-term

Avoid:

• Anywhere 304 is sufficient — the cost premium isn’t justified for non-chloride environments

Service life: 50-100+ years in chloride-exposed applications. 316 is the default specification for waterfront infrastructure; the increased material cost is trivial compared to the cost of replacing failed anchors in submerged or marine locations.

Side-by-Side Finish Comparison

Application Matrix — Pick by Use Case

If you know what you're anchoring rather than what environment you're in, look up your application below:

How Finish Affects Load Capacity

Different finish materials have different load-bearing characteristics. The summary:

• Carbon steel has the highest tension capacity at larger diameters (3/4", 1"). Material yield/tensile strength at those sizes outpaces stainless.
• Stainless steel (304 / 316) can have HIGHER shear capacity at smaller diameters (1/4", 3/8") due to higher tensile strength of the stainless alloys at those geometries. Crossover happens around 1/2"-5/8".
• Mechanically galvanized uses the same carbon steel base material as zinc-plated, so load values are identical to carbon steel zinc.
• 304 vs 316 load-wise are nearly identical — difference is corrosion resistance, not strength.

For per-diameter load value comparison, see our Wedge Anchor Pull-Out Strength & Load Tables.

Code-Compliance Note for Short-Length Variants

Frequently Asked Questions

What is the difference between 304 and 316 stainless wedge anchors?

Both are austenitic stainless steels. Type 304 (~18% chromium, 8% nickel) is general-purpose corrosion resistant and works for most outdoor and washdown environments. Type 316 adds 2-3% molybdenum to the alloy, dramatically improving chloride resistance. Use 316 within ~5 miles of saltwater, in pool decks and splash zones, in chemical processing with chloride exposure, or wherever de-icing salt is present. Use 304 for general exterior, food processing, and architectural applications.

Are mechanically galvanized wedge anchors as good as hot-dip galvanized?

Mechanically galvanized provides similar corrosion protection to hot-dip galvanized but without the dimensional concerns. Hot-dip galvanizing applies a thicker, less uniform coating that can fill anchor threads and interfere with fit-up. Mechanical galvanizing tumbles parts in zinc powder, producing a thinner but more dimensionally controlled coating. For most outdoor structural applications, MG is the practical choice over HDG for wedge anchors specifically.

Will a zinc-plated wedge anchor work outside?

Briefly. In dry, low-exposure outdoor conditions (under cover, in arid climates) zinc-plated anchors can last 5-10 years. In humid, coastal, or weather-exposed conditions, expect 1-5 years before significant corrosion. For any exterior installation longer than a few years, step up to mechanically galvanized at minimum, or 304 stainless for coastal/long-term work.

What does the 4SS or 6SS suffix on Simpson STB2 part numbers mean?

Simpson uses 4SS to indicate Type 304 stainless steel and 6SS to indicate Type 316 stainless steel. So SIMSTB2-50500 is the carbon steel zinc-plated 1/2 x 5 inch anchor; SIMSTB2-505004SS is the same anchor in Type 304 stainless; SIMSTB2-505006SS is Type 316. The suffix is the only thing that changes between finish variants of the same dimensional anchor.

Do stainless steel wedge anchors carry the same load as carbon steel?

Not exactly. At smaller diameters (1/4 inch, 3/8 inch), stainless can carry higher SHEAR values than carbon steel due to higher tensile strength of the stainless alloy. At larger diameters (3/4 inch, 1 inch), carbon steel carries higher TENSION values because of higher yield strength. The differences are usually within 10-15% at mid-range diameters (1/2 inch, 5/8 inch). For specific values per diameter, see our Pull-Out Strength & Load Tables.

Can I mix finish types on the same project?

Yes, and often you should. A typical mixed-use building might use carbon steel zinc for interior structural anchors, mechanically galvanized for exterior equipment pads, and 304 stainless for any architectural or coastal-exposed elements. The finishes are compatible (no galvanic concerns within the same fastener), and matching finish to exposure for each location optimizes both performance and cost.

Are stainless wedge anchors magnetic?

Type 304 and 316 are austenitic stainless steels and are essentially non-magnetic in their annealed state. Cold-working during manufacture (such as the threading process and the expansion clip forming) introduces some magnetic permeability, so a strong magnet may weakly attract a stainless wedge anchor. For applications requiring true non-magnetic fasteners (instrumentation, MRI rooms), specify additional non-magnetic verification from the manufacturer.

How do I tell what finish a wedge anchor is just by looking at it?

Carbon steel zinc plated has a dull silver or yellow tint. Mechanically galvanized has a matte gray, slightly textured appearance. 304 and 316 stainless are both bright shiny silver and look essentially identical to the eye — you can distinguish them only by the part number suffix (4SS vs 6SS) or by chemical/spectroscopic testing. If the part number is illegible, assume the more conservative material until verified.

Related Resources

• Wedge Anchor Selection & Installation Guide — sizing, install steps, common mistakes
• Wedge Anchor Pull-Out Strength & Load Tables — per-finish load comparison
• Wedge Anchor vs Sleeve Anchor Comparison
• Concrete Anchor Drill Bit & Hole Size Chart
• STB2 Material & Finish Selection Guide (PDF) — printable companion to this page
• Shop Simpson Strong-Bolt 2 wedge anchors in all finish options

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