Frequently Asked Questions

What chemicals does Nitocote SN1 resist that a standard epoxy like Nitocote EP202 cannot handle and how can a chemical engineer verify the resistance for a specific process chemical?

Nitocote SN1, as an epoxy novolac coating, extends chemical resistance significantly beyond the capability of standard bisphenol epoxy coatings like Nitocote EP202 for the following categories of chemicals that challenge standard epoxy systems. Concentrated mineral acids: EP202 provides good resistance to dilute acids (below 30 to 40 per cent concentration) but is progressively attacked by more concentrated acids, particularly above 50 per cent concentration where acid penetration into the standard epoxy network accelerates. Nitocote SN1 resists concentrated sulfuric acid at 70 to 96 per cent, concentrated hydrochloric acid at 30 to 37 per cent (fuming grade), and concentrated phosphoric acid at 85 per cent — these are the typical working concentrations in acid manufacturing and chemical dosing facilities. Aromatic solvents: EP202 has limited resistance to aromatic solvents (toluene, xylene, benzene, styrene) which swell and soften standard epoxy; SN1 resists these chemicals at normal temperatures because the higher cross-link density of the novolac network resists swelling and permeation by aromatic compounds. Ketones and esters at elevated concentrations: MEK, acetone, ethyl acetate, and similar chemicals at high concentration attack standard epoxy; SN1 provides significantly better resistance. To verify resistance of Nitocote SN1 to a specific process chemical not in the standard tested range, a chemical resistance immersion test should be performed: a fully cured SN1 sample (coated metal or concrete panel, minimum 7-day cure) is immersed in the specific chemical at the service temperature for 7, 14, and 28 days, and the change in hardness (pencil hardness or Shore D), weight change (indicating absorption or extraction), and visual condition (blistering, softening, discolouration) are measured. Fosroc India or Space Arc Engineering can assist with obtaining test data for specific chemicals encountered in Indian industrial facilities.

How is Nitocote SN1 applied to a concrete bund floor that will be used for concentrated sulfuric acid containment in a chemical plant?

Applying Nitocote SN1 to a concrete bund floor for concentrated sulfuric acid containment is a critical, safety-significant operation that requires meticulous surface preparation, controlled application conditions, and full coverage verification because any defect in the coating system (pinhole, holiday, thin spot, or disbonded area) creates a pathway for concentrated acid to contact and attack the concrete substrate — in concentrated sulfuric acid service, even a small coating holiday can result in rapid localised concrete destruction. The procedure is as follows. Surface preparation: the concrete bund must be cured for a minimum of 28 days; the surface is abrasive blasted to a minimum profile of 50 to 75 microns (International Blast Standard Sa 2.5 equivalent) to remove all laitance and create an open pore profile for SN1 penetration and adhesion; all corners and bund floor-to-wall junctions must be filleted with a compatible epoxy filler mortar to form a radius of at least 25 mm — acid pooling in sharp internal corners causes stress concentration in the coating that leads to premature failure at these critical locations; all surface cracks must be saw-cut and filled with compatible epoxy sealing compound; and the surface moisture must be below the maximum allowable for SN1 application. Application: the first coat of SN1 is applied by brush to ensure penetration into prepared surface pores (brush application provides better pore penetration than roller for the first coat); subsequent coats are applied by roller or brush at the specified inter-coat interval, building the total DFT to 800 to 1,000 microns in minimum three coats; each coat is holiday-tested with a DC spark tester after cure before the next coat is applied; the final coat is the definitive holiday test — the entire bund floor and wall coating is holiday-tested at 100 per cent coverage before the bund is accepted and placed in service. The entire application process should be carried out by a specialist chemical-resistant coating applicator with experience in acid-resistant lining work.

What is the minimum curing time for Nitocote SN1 before the coated area can be put into chemical service with concentrated sulfuric acid?

The minimum cure time for Nitocote SN1 before placing the coated concrete into concentrated sulfuric acid service is significantly longer than the curing time before the area can be walked on or the next coat applied. For full chemical resistance to develop, the novolac epoxy network requires full cure — which for most epoxy novolac systems at normal Indian ambient temperatures (25 to 35 degrees Celsius) is a minimum of 7 days after the final coat is applied. This 7-day post-application cure is the minimum time required before immersion in concentrated acid because: the initial cure of epoxy coatings (measured by hardness and tack-free times of 6 to 24 hours) represents only the early-stage cross-linking of the epoxy network — at early cure, the polymer network still has reactive groups that have not yet cross-linked and that would be susceptible to attack by concentrated acid; the full cross-link density that provides the maximum chemical resistance of the novolac network develops over 5 to 14 days of ambient temperature cure; and placing a not-fully-cured SN1 coating into concentrated acid service allows acid to penetrate the incompletely-cross-linked network more rapidly, potentially causing premature failure. To achieve the fastest possible high-quality cure (for projects with tight programme requirements), post-cure at elevated temperature can be used: heating the coated concrete to 50 to 60 degrees Celsius for 16 to 24 hours (using industrial air heaters or heat guns in an enclosed tent over the bund) significantly accelerates cross-linking and can achieve the equivalent of 7 days of ambient cure within 24 to 48 hours of post-curing. Heat post-curing is common practice in chemical plant maintenance where production shutdown periods are limited. Confirm the specific Nitocote SN1 post-cure schedule with Fosroc technical support or Space Arc Engineering before implementation.