PPG SigmaZinc 158 is a two-component, moisture-curing zinc (ethyl) silicate anti-corrosive primer for structural steel.  When suitably topcoated provides excellent corrosion protection for steel substrates up to 540°C (1000°F). Complies with the compositional requirements of SSPC-Paint 20, Level 2, PPG SigmaZinc 158 also boasts good impact and abrasion resistance.

Top Features & Benefits

• Certificate for ASTM A-490 class 'B' for slip coefficient
• Suitable as a system primer in various paint systems based on unsaponifiable binders
• Galvanic action eliminates sub-film corrosion
• Can withstand substrate temperatures from –90°C (–130°F) up to 400°C (750°F), under normal atmospheric exposure conditions
• Good low-temperature curing
• Must not be exposed to alkaline (more than pH 9) or acidic (less than pH 5.5) liquids

Preparation & Application

Recommended Substrate Conditions and 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

Atmospheric Exposure Conditions

• Steel; blast cleaned to ISO-Sa2½, blasting profile 40 – 70 µm (1.6 – 2.8 mils)
• Steel with approved zinc silicate shop primer; pre-treated to SPSS-Pt3

Substrate Temperature and Application Conditions

Substrate temperature during application and curing down to -5°C (23°F) is acceptable; provided the substrate is free from ice and dry. Substrate temperature during application up to 50°C (122°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 81:19. 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

Induction Time

None

Pot Life

12 hours at 20°C (68°F)

Air Spray

Recommended thinner: PPG Thinner 90-53

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: PPG Thinner 90-53

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: PPG Thinner 90-53

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

PPG Thinner 90-53

Upgrading

This is only valid for spray application. If the DFT is below specification and an extra coat of SIGMAZINC 158 has to be applied, SIGMAZINC 158 should be thinned down with 25 – 50% PPG Thinner 90-53, in order to obtain a visible wet coat that remains wet for some time.

Safety Precautions

For paint and recommended thinners see INFORMATION SHEETS 1430, 1431 and relevant Material Safety Data Sheets. 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.

Product Data

References

• Safety Indicators (information sheet 1430)
• Safety in Confined Space and Health Safety, Explosion Hazard - Toxic Hazard (information sheet 1431)