PPG Dimetcote 9 (also known as Sigmazinc 9) is a two-component, moisture-curing zinc (ethyl) silicate coating for structural steel. Under normal atmospheric conditions, Dimetcote 9 can withstand substrate temperatures from –90°C (–130°F) up to 400°C (750°F). As an anti-corrosive primer for structural steel, Dimetcote 9 also offers good impact and abrasion resistance .

Although the use of a brush to apply Dimetcote 9 is recommended only for touch-up and spot repair, Dimetcote should be appled by air or airless spray.

Must not be exposed to alkaline (more than pH 9) or acidic (less than pH 5.5) liquids.

This is a solvent-borne paint and care should be taken to avoid inhalation of spray mist or vapor, as well as contact between the wet paint and exposed skin or eyes.

Top Features & Benefits

• Suitable as a system primer in various paint systems based on unsaponifiable binders
• When suitably topcoated provides excellent corrosion protection for steel substrates up to 540°C (1000°F)
• Good low-temperature curing
• Good impact and abrasion resistance
• Specified for structural joints according to ASTM A325 or A490 Bolts RCSC specification, Class B
• Complies with the compositional requirements of SSPC-Paint 20, Level 1
• Flat Finish
• Used on Adelaide Oval Cricket Ground, Riverbank Stand, Adelaide, South Australia

Product Data

Preparation & Application

Recommended Substrate Conditions & Temperatures

Immersion Exposure

• Steel; blast cleaned to ISO-Sa2½, blasting profile 40 – 70 µm (1.6 – 2.8 mils)
• Steel with approved zinc silicate shop primer; sweep blasted to SPSS-Ss, welds, rusty and damaged areas blast cleaned to ISO-Sa2½
• Existing pipelines may have to be cleaned first by scraper pigs and solvents

Atmospheric Exposure Conditions

• Steel; blast cleaned to ISO-Sa2½ or minimum SSPC SP-6, blasting profile 40 – 70 µm (1.6 – 2.8 mils)
• Steel with approved zinc silicate shop primer; pretreated to SPSS-Pt3

Substrate Temperature & Application Conditions

• Substrate temperature during application and curing down to -18°C (0°F) is acceptable; provided the substrate is free from ice and dry
• Substrate temperature during application up to 55°C (131°F) is acceptable
• Substrate temperature during application and curing should be at least 3°C (5°F) above dew point
• Relative humidity during curing should be above 50%

Instructions For Use

Mixing ratio by volume: binder to zinc powder 77:23.

Many of PPG's zinc silicates are supplied as two-pack materials consisting of a container with pigmented binder and a drum containing a bag of zinc powder. To ensure proper mixing of both components, the instructions given below must be followed:

• To avoid lumps in the paint do not add the binder to the zinc powder
1. Take the bag with zinc powder out of the drum
2. Shake the binder in the jerrycan a few times to reach a certain degree of homogenization
3. Pour about 2/3 of the binder into the empty drum
4. With the jerrycan now reduced in weight and containing more free space, shake it vigorously to obtain a homogeneous mix with no deposits left on the bottom, and add this to the drum
5. Add the zinc powder gradually to the pigmented binder in the drum and, at the same time, continuously stir the mixture by using a mechanical mixer (keep the speed low)
6. Stir the zinc dust powder thoroughly through the binder (high speed) and keep stirring until a homogeneous mixture is obtained
7. Strain mixture through a 30 – 60 mesh screen
8. Agitate continuously during application (low speed). The use of a dedicated pump with a constant agitation for a zinc silicate coating is recommended
• Note: At application temperature above 30°C (86°F) addition of max 10% by volume of THINNER 90-53 may be necessary

Air Spray

Recommended thinners

• THINNER 90-53
• THINNER 21-06 (AMERCOAT 65)
• THINNER 21-25 (AMERCOAT 101) FOR > 60°F (15°C)

Volume of thinner

• 0 - 10%, depending on required thickness and application conditions

Nozzle orifice

• 2.0 mm (approx. 0.079 in)

Nozzle pressure

• 0.3 MPa (approx. 3 Bar; 44 p.s.i.)

Note: A dedicated pump for a zinc silicate coating with constant agitation must be used

Airless Spray

Recommended thinner

• THINNER 90-53
• THINNER 21-06 (AMERCOAT 65)
• THINNER 21-25 (AMERCOAT 101) FOR > 60°F (15°C)

Volume of thinner

• 0 - 10%, depending on required thickness and application conditions

Nozzle orifice

• Approx. 0.48 – 0.64 mm (0.019 – 0.025 in)

Nozzle pressure

• 9.0 - 12.0 MPa (approx. 90 - 120 bar; 1306 - 1741 p.s.i.)

Note: A dedicated pump for a zinc silicate coating with constant agitation must be used

Brush/Roller

• Only for touch-up and spot repair
• Roller application is not recommended

Recommended thinner

• THINNER 90-53
• THINNER 21-06 (AMERCOAT 65)
• THINNER 21-25 (AMERCOAT 101) FOR > 60°F (15°C)

Volume of thinner

• 5 – 15%

Note: Apply a visible wet coat with a max. dft of 25 µm (1.0 mils)|same for subsequent coats in order to obtain the required dft

Cleaning Solvent

• THINNER 90-53
• THINNER 90-58 (AMERCOAT 12) OR THINNER 21-06 (AMERCOAT 65)

Upgrading

• This is only valid for spray application
• If the DFT is below specification and an extra coat of DIMETCOTE 9 / SIGMAZINC 9 has to be applied, it should be thinned down with 25 – 50% THINNER 90-53, in order to obtain a visible wet coat that remains wet for some time

Additional Data

Notes:

• Maximum DFT when brushing: 35 µm (1.4 mils)
• Above 150 µm (6.0 mils) mudcracking can occur
• Highly pigmented zinc silicate primers produce dry films with void spaces in between the particles

Notes:

• For recoating with itself to take required dft, recommend to apply within 2 days before full cure. No minimum recoating interval limitation for itself.
• To confirm cure to topcoat, conduct a MEK rub test per ASTM D4752. A rating of 4 or higher is sufficient for topcoating
• For measuring of the curing, the MEK rub test according to ASTM 4752 is a suitable method: after 50 double rubs with a cloth soaked in MEK (or alternatively THINNER 90-53) no dissolving of the coating should be observed
• Curing/recoating time will be shortened by the increase of humidity, please contact regional technical service team for details
• A mist coat / full coating application technique is required when topcoating to prevent application bubbling. Ensure dry spray is removed from the surface
• DIMETCOTE 9 / SIGMAZINC 9 is a moisture curing zinc silicate, this means that it only cures after sufficient take up of water from the atmosphere during and after application; it is recommended that relative humidity and temperature are measured during the curing time
• When curing conditions are unfavorable or when reduced overcoat times are desired, curing can be accelerated 4 hours after application by: [1] Wetting or soaking with water, keeping the surface wet for the next 2 hours, followed by drying; [2] Wetting or soaking with a 0.5% ammonia solution, followed by drying
• Maximum interval is only unlimited when the surface is free from any contamination

Notes:

• DIMETCOTE 9 / SIGMAZINC 9 is a moisture curing zinc silicate, this means that it only cures after sufficient take up of water from the atmosphere during and after application
• It is recommended that relative humidity and temperature are measured during the curing time
• Relative humidity during curing recommended to be above 50%
• Adequate ventilation must be maintained during application and curing (please refer to INFORMATION SHEETS 1433 and 1434)