Project Overview
Location: Hoopstad, Free State
Industry: Fertilizer storage and handling
Environment: High pH, corrosive internal atmosphere
Product used: Si‑COAT 579 CM
Application date: January 2025
Corrosion Coating for Fertilizer Plants: A Real-World Trial in Hoopstad, Free State
Steel structures inside fertilizer storage facilities face one of the harshest corrosion environments in South African industry. Ammonia-based and high-pH fertilizer materials attack steel continuously, and conventional maintenance cycles rarely keep pace with the rate of degradation. This case study documents a trial application of SI-COAT 579 CM as a corrosion coating for a fertilizer plant in Hoopstad, Free State, carried out in January 2025 under live operating conditions.
The Problem: Continuous Corrosion in a High-pH Environment
The facility stores bulk fertilizer, and the high pH content of the material creates a persistently aggressive atmosphere for the internal steel structure. Previous maintenance measures had not delivered long-term corrosion control. The structure required repeated intervention, with no coating solution proving sustainable under continuous exposure.
Shutting down the facility or replacing the steel structure was not feasible. Any solution had to be applied while the plant remained operational and had to perform under ongoing fertilizer exposure.
The Trial: SI-COAT 579 CM Applied to Structural Columns
The client requested a controlled trial before committing to a full application. Selected structural columns were prepared by removing loose corrosion using a flap wheel and wire brush. No primer was applied. SI-COAT 579 CM was then coated directly onto the prepared steel surface in Traffic White.
The trial was designed to answer a straightforward question: does the coating hold under real operating conditions?
Three Months Later: Discolouration Investigated
After three months, discolouration appeared at the base of certain columns. A full investigation was conducted to determine whether this indicated coating failure.
The investigation found that the discolouration was not caused by failure of the coating itself. Corrosion runoff from uncoated steel above the trial area had tracked down the columns and collected at the base, settling in rough areas where historic corrosion had previously eroded the steel surface. The coating remained intact. The discolouration was surface-only and wiped off with a damp cloth.
This outcome carries an important technical point: surface discolouration on a coated structure does not automatically indicate that the coating has failed. The source of contamination matters, and in this case it originated above the coated section.
The Hopper: A High-Risk Area
The hopper structure showed advanced corrosion and was identified as a priority zone. Before TSS introduced SI-COAT 579 CM to the site, the client had already begun applying red oxide primer to parts of the hopper in preparation for coating.
TSS used this as an opportunity to run a direct comparison. On sections where only sandblasting had been performed — with no red oxide primer — SI-COAT 579 CM was applied directly to the prepared steel. After three months, those unprimed sections showed no signs of corrosion. The client noted the result and acknowledged that the primer step had been unnecessary.
The hopper trial confirmed what TSS already knew about SI-COAT 579 CM: adequate surface preparation is sufficient. Primer is not required.
Six-Month Results
At the six-month mark, all areas treated with SI-COAT 579 CM continued to show no active corrosion. The coating performed under continuous fertilizer exposure without primer, without abrasive blasting, and without facility shutdown.
The results confirmed the suitability of SI-COAT 579 CM as a corrosion coating for fertilizer plant environments in South Africa.
Why SI-COAT 579 CM Works in This Environment
SI-COAT 579 CM is a silicone-based corrosion maintenance coating formulated for aggressive industrial conditions. Its chemistry allows it to bond directly to prepared steel and to tolerate chemical exposure that conventional coatings cannot sustain long-term. It does not require a primer on properly prepared surfaces, which reduces application cost and complexity — particularly relevant in operational facilities where preparation access is limited.
The product is available in South Africa through TSS, the exclusive Sub-Saharan Africa distributor for CSL Silicones.
Key Takeaways from the Hoopstad Trial
Surface discolouration is not evidence of coating failure — always investigate the source before drawing conclusions. Primer is not required when surface preparation removes loose corrosion adequately. SI-COAT 579 CM can be applied in live operating environments without facility shutdown. Real-world monitoring over a sustained period is the only reliable way to validate coating performance. The results confirmed the suitability of SI-COAT 579 CM as a corrosion coating for fertilizer plant environments in South Africa.
FAQ
Is a primer required before applying SI-COAT 579 CM to corroded steel?
No. The Hoopstad trial confirmed that SI-COAT 579 CM can be applied directly to steel prepared with a flap wheel or wire brush, without red oxide or any other primer. Areas treated this way showed no corrosion after three months under fertilizer exposure.
Can SI-COAT 579 CM be applied while a fertilizer plant is operational?
Yes. The Hoopstad trial was carried out while the facility remained in operation. The coating does not require shutdown or controlled environment conditions for application.
What caused the discolouration seen at the base of the columns after three months?
The discolouration was traced to corrosion runoff from uncoated steel above the trial area. The coating itself was undamaged. The staining was removed with a damp cloth and was not evidence of coating failure.
Where can I source SI-COAT 579 CM in South Africa?
TSS — Technical Solutions Supplies — is the exclusive Sub-Saharan Africa distributor for CSL Silicones. Contact TSS directly for product supply, technical support, and application guidance.