What surfaces can Carbomastic 15 be applied to?

Carbomastic 15 can be applied to steel (non-immersion and immersion), rusted steel prepared to SSPC-SP2 or SP3 minimum, previously painted surfaces in tight condition, non-ferrous metals, and galvanized steel. It is self-priming and suitable as a topcoat over most tightly adhered existing coatings.

What is the mix ratio for Carbomastic 15?

Carbomastic 15 uses a 1:1 mix ratio by volume (Part A to Part B). Power mix each component separately before combining. Do not mix partial kits.

What is the pot life of Carbomastic 15?

Carbomastic 15 has a pot life of 2 hours at 75 degrees F (24 degrees C) and approximately 1 hour at 90 degrees F (32 degrees C). Higher temperatures significantly reduce working time.

Carbomastic 15 Epoxy Mastic Kit

Q: What is the coverage rate for Carbomastic 15?

Carbomastic 15 covers approximately 481 sq ft per gallon at 3 mils DFT and 144 sq ft per gallon at 10 mils DFT (theoretical). Over existing coatings, the recommended DFT is 3 to 5 mils. For severe exposures on bare or rusted steel, 7 to 10 mils is recommended.

Q: Can Carbomastic 15 be used under insulation?

Yes. Carbomastic 15 is rated for corrosion under insulation (CUI) service up to 400 degrees F (204 degrees C). It is also suitable for direct application to uninsulated hot surfaces up to 300 degrees F (149 degrees C). Discoloration may be observed above 180 degrees F (82 degrees C) but does not affect performance.

Q: Can Carbomastic 15 be topcoated?

Yes. Carbomastic 15 can be topcoated with acrylics, alkyds, epoxies, polyaspartics, polyurethanes, and siloxanes depending on exposure requirements. Maximum recoat time is 30 days for epoxies and 90 days for polyurethanes at 75 degrees F.

Carbomastic 15 Epoxy Mastic Kit

by Carboline

$626.48 - $2,641.50

$626.48

$626.48 - $2,641.50

$626.48

Carbomastic 15 by Carboline is an aluminum-pigmented, high-solids epoxy mastic coating designed for superior barrier protection and corrosion resistance. It performs well over minimally prepared steel substrates, rusted surfaces, or tightly adhered existing coatings, and is suitable as a topcoat or for field touch-up of zinc-rich primers and galvanized steel.
It can also be used under insulation on hot surfaces up to 300°F (150°C).

Provides unmatched levels of barrier protection and corrosion resistance over existing finishes and rusted or SSPC-SP2 or SP3-cleaned steel.

FULL COLLECTION OF CARBOLINE COATINGS FOUND HERE >

CARBOMASTIC 15 FEATURES:

Superior Barrier Protection: Incorporates lamellar aluminum flakes for unmatched corrosion resistance.

Minimal Surface Prep: Performs excellently over minimally prepared steel, rusted surfaces, or tightly adhered coatings.

Versatility: Acts as a topcoat, primer, or touch-up for zinc-rich primers and galvanized steel, with a low-temperature cure option (Carbomastic 15 FC).

High Temperature Resistance: Suitable for use under insulation on surfaces up to 300°F (150°C), with discoloration above 180°F (82°C) not affecting performance.

Durability: Demonstrates excellent abrasion, salt spray, and water resistance, with flexibility and impact resistance as per ASTM tests.

CARBOMASTIC 15 SOLD IN 2-GALLON & 10-GALLON KIT, INCLUDING PARTS A & B.

Product type: Epoxy Mastic
Applied via: Conventional Spray, Airless Spray, Brush, or Roller
Mixing: 1:1 Ratio Parts A to B
Compatible Thinners: Thinner No. 10 normal conditions, also 2, 15, 76, 229, 230
May be coated with Acrylics, Epoxies, Alkyds, or Polyurethanes depending on exposure and need.

Contact our customer support today to discuss your project:
(800) 567-5358

**Red (M500) is available for use as a contrasting primer in multiple coat applications, but should always be topcoated.

Quantity

Area to cover (sq ft)

Application method

Coats

DFT per coat (mils)

Kit size

Color

Carbomastic 15 is a self-priming mastic — no separate primer is required over properly prepared steel or existing coatings. It can serve as a standalone system, a primer under a urethane topcoat, or a direct topcoat over tightly adhered existing coatings. See the Coating Systems section below for common configurations.

Compatible Thinners

Thinner	Application	Max Rate
Thinner 10 ›	Normal spray / brush / roller (preferred)	32 oz/gal (25%)
Thinner 230	Hot substrates up to 200°F (93°C)	32 oz/gal (25%)
Thinner 72	Hot or windy conditions	Per PDS
Thinner 76	Non-photochemically reactive thinner	Per PDS
Thinner 236E	Exempt thinner (VOC-restricted areas)	Per PDS
Thinner 2 ›	Equipment cleanup only	N/A — cleanup only

Thinner 10 is the preferred application thinner for normal conditions. Use of thinners not supplied or recommended by Carboline may adversely affect performance and void the product warranty.

Recommended Coating Systems

Single-Coat System — Maintenance / Minimal Surface Prep

Primer + Finish — You Are Here Carbomastic 15 7–10 mils DFT · self-priming over SP2/SP3 or rusted steel

Two-Coat System — Industrial Maintenance with UV Finish

Primer / Intermediate — You Are Here Carbomastic 15 7–10 mils DFT · over SP2/SP3 or rusted steel

→

UV-Stable Topcoat Carbothane 134 HG 2–3 mils DFT · high-gloss, UV-stable finish

Overcoat System — Applied Over Existing Coatings

Existing Coating Tightly Adhered Finish min. 3A per ASTM D3359 · clean and deglossed

→

Maintenance Topcoat — You Are Here Carbomastic 15 3–5 mils DFT · no blast required

Frequently Purchased Together

Carboline Thinner No. 10

Preferred spray, brush, and roller thinner for Carbomastic 15. Up to 25% addition rate.

From $125.25 / gal

Shop Now

Carboline Thinner No. 2

Equipment and spray line cleanup after Carbomastic 15 application.

From $129.87 / gal

Shop Now

Carbothane 134 HG

UV-stable high-gloss polyurethane topcoat. Apply over Carbomastic 15 when color and gloss retention are required outdoors.

From $292.27 / gal kit

Shop Now

Carboguard 890 self-priming epoxy — used alongside Carbomastic 15 in multi-coat systems

Carboguard 890 Epoxy

Self-priming epoxy for chemical resistance and intermediate coat applications. Often used in systems alongside Carbomastic 15.

From $419.48 / 2-gal kit

Shop Now

Product Specs — Carbomastic 15

Carbomastic 15 — High-Solids Aluminum Epoxy Mastic Coating by Carboline.
Aluminum-pigmented, low-stress, high-solids epoxy mastic with a proven field history. Incorporates lamellar aluminum pigment for superior barrier protection. The pioneer mastic coating in industrial maintenance markets — engineered to perform over minimal surface preparation, rusted steel, and tightly adhered existing coatings. Available in 2-gallon and 10-gallon kits.

Carbomastic 15 by Carboline

VOC Compliant — AIM Regulations • 90% Solids by Volume • Accepts SSPC-SP2 / SP3 Minimum Surface Prep

Need a project quote? Request Online

Questions? Call (800) 567-5358 — Mon–Fri 8AM–5PM EST

Shipping Map — Carboline Delivery Timing

Carboline US regional warehouse shipping map showing typical delivery transit zones by destination — Typical transit times vary by destination zone.

Shipping & Availability

Call (800) 567-5358 for pricing and logistics questions.

Carbomastic 15 ships from Carboline regional warehouses nearest to your location. Each kit includes Part A and Part B.

Most orders ship within 2–3 business days of order placement. Transit times vary by destination zone — see shipping map.

Available sizes: 2-gallon kit (Part A + B) • 10-gallon kit (Part A + B)

Colors available: Aluminum (C901) • Red (M500) — Red is for use as a contrasting primer and must always be topcoated.

Carbomastic 15 Coverage Rates

DFT Range: 3–5 mils over existing coatings • 7–10 mils for severe exposures. Do not exceed 10.0 mils in a single coat.

DFT per Coat	Theoretical	Practical (Airless)	Typical Use
3 mils (76 µm)	481 ft²/gal	~385 ft²/gal	Over existing coatings — maintenance
5 mils (127 µm)	289 ft²/gal	~231 ft²/gal	Over existing coatings — enhanced protection
7 mils (178 µm)	206 ft²/gal	~165 ft²/gal	Severe exposure — bare or rusted steel
10 mils (254 µm)	144 ft²/gal	~115 ft²/gal	Maximum single coat — severe exposure
1 mil (25 µm)	1,444 ft²/gal	—	Theoretical reference (90% solids by vol.)

Practical yield assumes ~20% airless spray loss. Actual coverage varies with surface profile, temperature, and technique.
Source: Carboline Carbomastic 15 PDS, May 2023

Mixing Instructions

Mix Ratio: 1:1 by volume (Part A to Part B)

Power mix Part A separately until uniform. Power mix Part B separately. Combine at the 1:1 ratio and power mix together until fully blended with no streaks. Do not mix partial kits.

Pot life: 2 hours at 75°F (24°C) • Approx. 1 hour at 90°F (32°C). Mix only what you can apply within the pot life window.

Thinning

Condition	Thinner	Max Rate
Normal spray conditions	Carboline Thinner 10	32 oz/gal (25%)
Hot substrates up to 200°F (93°C)	Carboline Thinner 230	32 oz/gal (25%)
Hot or windy conditions	Carboline Thinner 72	Per PDS
Non-photochemically reactive needed	Carboline Thinner 76	Per PDS
Exempt thinner needed	Carboline Thinner 236E	Per PDS
Equipment cleanup	Carboline Thinner 2 or Acetone	N/A — cleanup only

Use of thinners other than those recommended and supplied by Carboline may adversely affect product performance and void the product warranty.

Cure Times at a Glance

Temperature	Dry to Recoat	Full Cure
50°F (10°C)	5 days	15 days
60°F (16°C)	3 days	10 days
75°F (24°C)	24 hours	5 days
90°F (32°C)	18 hours	3 days

Based on 5.0–7.0 mil DFT. Higher build or cooler temperatures extend cure times.

Compatible Substrates & Surface Preparation

See the full product data sheet for complete surface preparation guidelines.

Substrate	Surface Preparation Requirement
Steel (Non-Immersion)	SSPC-SP6 Commercial Blast recommended for maximum protection. SSPC-SP2 (Hand Tool), SSPC-SP3 (Power Tool), SSPC-SP7 (Brush-Off), or SSPC-SP14 also acceptable. Angular surface profile 2.0–3.0 mils.
Steel (Immersion Service)	SSPC-SP10 Near White Blast required. Angular surface profile 2.0–3.0 mils.
Previously Painted Surfaces	Clean and lightly sand or abrade to roughen and degloss. Existing coating must achieve a minimum 3A rating per ASTM D3359 adhesion test.
Non-Ferrous Metals	Dense angular surface profile 1.5–3.0 mils via abrasive blasting. SSPC-SP16 for atmospheric; SSPC-SP17 for immersion service.
Galvanized Steel / Zinc Primers	Excellent choice for field touch-up over inorganic zinc primers and galvanized surfaces in atmospheric service.

Typical Applications

Application / Environment	Details
Industrial Maintenance	Bridges, structural steel, tanks, and equipment where minimal surface prep is required. Applies over SSPC-SP2/SP3 cleaned or rusted steel.
Refinery and Chemical Tanks	Maintenance coating program anchor for storage tanks. Enables faster, more efficient programs over time-intensive systems that require full blast to bare steel.
Corrosion Under Insulation (CUI)	Rated for CUI service up to 400°F (204°C). Also suitable for direct application to uninsulated hot surfaces up to 300°F (149°C).
Marine — Hulls and Offshore	Applied as a primer to ocean supply vessels and offshore structures in corrosive saltwater environments. Proven 12-plus year field history on Gulf of Mexico deployments.
Topcoat Over Existing Coatings	Suitable as a topcoat for most tightly adhered existing coatings. High-solids resins penetrate without attacking or degrading the underlying film.
Zinc Primer Touch-Up / Galvanized Steel	Excellent field touch-up choice over zinc-rich primers and galvanized steel in atmospheric service.

What to Know Before You Order

Minimum temperature: Do not apply below 50°F (10°C) surface or ambient temperature. For cold-weather applications, see Carbomastic 15 FC — rated for application down to 35°F (1.7°C).
Maximum single-coat DFT: Do not exceed 10.0 mils (254 µm) per coat. Higher build requires longer cure times and can cause premature failure.
Do not mix partial kits. The 1:1 ratio must be maintained precisely for a full cure.
Cannot be holiday tested. This product contains conductive pigments and cannot be electrically tested for pinholes after application.
Red color must be topcoated. Red (M500) is a contrasting primer for multi-coat systems only and must always receive a topcoat.
Recoat window: Maximum 30 days for epoxy topcoats, 90 days for polyurethanes at 75°F. If exceeded, sweep blast before recoating.

Fireproofing compatibility: Recoat intervals may differ when applying Carbomastic 15 under Carboline intumescent fireproofing. Consult Carboline Technical Service before applying intumescent topcoats.

Frequently Asked Questions — Carbomastic 15

What is the coverage rate for Carbomastic 15?

At 3 mils DFT over existing coatings, Carbomastic 15 covers approximately 481 ft²/gal theoretical and ~385 ft²/gal practical (airless spray). At 5 mils: ~289 ft²/gal theoretical. At 10 mils (maximum single coat): ~144 ft²/gal theoretical. See the coverage table above for practical airless spray yields at each thickness.

What is the mix ratio and pot life?

Mix ratio is 1:1 by volume (Part A to Part B). Pot life is 2 hours at 75°F (24°C) and approximately 1 hour at 90°F (32°C). Do not mix partial kits.

Does Carbomastic 15 require blast cleaning?

No full blast is required for non-immersion service. Carbomastic 15 performs over SSPC-SP2 (Hand Tool) or SSPC-SP3 (Power Tool) cleaned and even rusted steel. SSPC-SP6 Commercial Blast is recommended for maximum protection. SSPC-SP10 Near White Blast is required for immersion service only. This makes it a strong choice for maintenance projects where downtime and blast access are limited.

Can Carbomastic 15 be used under insulation?

Yes. Carbomastic 15 is rated for corrosion under insulation (CUI) service up to 400°F (204°C) and for direct application to uninsulated hot surfaces up to 300°F (149°C). Some discoloration may be visible above 180°F (82°C) but does not affect performance. For application to substrates above 200°F (93°C), thin with Carboline Thinner 230 at approximately 25%.

Can Carbomastic 15 be topcoated?

Yes. Carbomastic 15 accepts topcoats of acrylics, alkyds, epoxies, polyaspartics, polyurethanes, and siloxanes. Maximum recoat time is 30 days for epoxies and 90 days for polyurethanes at 75°F. If that window is exceeded, the surface must be sweep blasted before recoating.

What kit sizes are available?

Carbomastic 15 is available in 2-gallon kits and 10-gallon kits, each containing Part A and Part B. Use the coverage table above to estimate your project requirements, then round up. Do not mix partial kits.

What is the shelf life?

Both Part A and Part B have a minimum shelf life of 36 months when stored at 75°F (24°C) in original unopened containers. Store between 45–110°F (7–43°C) at 0–90% relative humidity, indoors.