What plating and pickling demand of a floor

Grating in plating and pickling shops faces acid mist, splashes, drips and washdown at the same time. Around pickling tanks there is often mist from hydrochloric or sulfuric acid; around plating tanks there are chromic acid, sulfuric acid and metal salts. The floor stays wet, and dropped workpieces and jigs add impact.

These media are not at one concentration. Splash at the tank edge may be strong, washdown on the floor is diluted, and acid mist condensing on the grating sits between the two. Treat concentrated liquid, mist and dilute wash water separately at selection stage, and design to the most severe case.

Temperature also moves. Cold pickling, heated pickling and warm plating baths change the corrosion rate. Resin resistance grades are usually quoted at ambient temperature; as temperature rises the usable range narrows, and the resin maker's data governs.

Choosing the resin

The chemical resistance of FRP grating comes mainly from the resin; the glass fibre carries load but does not resist attack. Common resins are orthophthalic, isophthalic and vinyl ester. Orthophthalic is the lowest cost and suits ordinary atmosphere and mild attack; isophthalic is better in water and moderate acid or alkali; vinyl ester holds up better in strong acids, oxidizing media and higher temperatures.

Plating and pickling are severe duties, so vinyl ester is usually the first candidate. Sulfuric acid, hydrochloric acid and mixed acids hydrolyse ester linkages to different degrees, and the closed end groups of vinyl ester give better hydrolysis stability. Check the specific grade and resistance table against the resin maker's data; do not judge by resin family alone.

The surface veil matters too. Where the surface is only resin and coarse roving, media can seep along the fibre interface. A product with a surface veil or resin-rich layer has a denser skin and better resistance to permeation and ultraviolet. State on the order whether a veil is required instead of assuming all panels are the same.

Fire retardance and chemical resistance sometimes conflict. Additive flame retardants can reduce chemical resistance, while reactive flame-retardant resins affect it less. Where the shop also has a fire requirement, ask the supplier for both the fire rating and the chemical data, and do not let one document stand in for the other.

Concentration and temperature traps

Sulfuric acid behaves very differently with concentration. Dilute sulfuric acid attacks most resins more strongly, while concentrated acid at room temperature may passivate some resin surfaces; raise the temperature and both pictures change again. It is not safe to assume that resistance to concentrated acid means resistance to dilute acid.

Hydrochloric acid is volatile, and its mist stays on the top and underside of grating for long periods. Attack tends to concentrate at the surface and at cut edges, so edge sealing and the surface veil matter more than thickness.

Mixed acids are harder to judge. A pickling bath may contain sulfuric acid, hydrochloric acid and inhibitors at once, and a plating bath adds metal ions and additives. Components can accelerate each other's attack, and reading one acid's resistance table alone underestimates the risk. Where the duty is complex, run a coupon test or ask the supplier for cases in the same medium. To screen grating by medium, see chemical-resistant grating by medium

Slip resistance and cleanability

Floors in pickling and plating areas are permanently wet, so slip resistance is a basic requirement. The gritted surface of FRP grating is more reliable wet than a smooth finish, but the grit becomes contaminated with acid and must be rinsed clean.

The other problem with an anti-slip surface is liquid retention. Grit and pattern recesses hold acid, and without thorough rinsing the residue keeps attacking the resin. The rougher the surface, the more it needs high-pressure washing and a neutralising step.

Cleanability and slip resistance have to be balanced. Open grating drains and washes easily but relies on surface treatment for grip; gritted grating grips well but is harder to clean. Plating shops usually need both, so use a gritted surface on walkways and a more open pattern at tank edges and drain areas.

Cut edges and drilled holes are the weak points. Seal them with compatible corrosion-resistant resin immediately after site work; never leave glass fibre exposed. The sealant must be compatible with the grating resin, or it will fail before the panel does.

Embedded items and fasteners

Under grating in a plating shop sit tanks, pipework and busbars, and the supports and fasteners are often metal too. Carbon steel rusts quickly in acid mist, and rust water contaminates both bath and floor, so use 316 stainless or a material compatible with the medium.

Stainless is not universal either. Hydrochloric acid and chloride media cause pitting and stress corrosion, and 316 is not suitable in concentrated hydrochloric acid. Select fastener material against the actual medium; do not assume stainless is automatically safe.

Where metal meets FRP, crevices form easily. Liquid sits in the gap, oxygen is depleted and corrosion accelerates. Fit an isolating pad or sealant during installation to fill the gap and keep acid out.

Fixing positions should be settled at design stage. Drilling on site damages the edge seal and the support, and a site-applied seal is usually poorer than a factory one. Connection plates, bolt holes and drainage slope on the support beams should be considered together. To match resin and support detail to the medium, see FRP grating for chemical plants

Supports and spans

FRP grating is less stiff than steel grating, so span is governed by allowable deflection rather than strength alone. Trolleys and tanks move through pickling shops, and both concentrated and dynamic loads have to be counted.

Support spacing and direction affect how the panel carries load. Bearing bars should run with the main walking direction, and support spacing should follow the maker's load table. Where the span is too long, add supports or use a deeper panel rather than laying a thin sheet on top.

The supports themselves must resist corrosion. Concrete beams carbonate in acid mist, and steel beams need coating or FRP encapsulation. Support life and grating life should match, or the support will fail before the grating does.

Installation and routine care

Check support level and slope before laying panels. Grating should bear continuously on its supports, not on a few packing points, or the load concentrates and cracks develop over time.

Fixings must allow thermal movement. FRP expands more than steel, and long panels in a shop with wide temperature swings will grow and shrink; locking every fixing builds up internal stress. The usual arrangement is fixed at one end and sliding at the other.

Routine care is mainly rinsing and inspection. Flush acid residue promptly, especially on the underside and at support contact faces. Check edge seals, fasteners and visible cracks quarterly, and ask the supplier to assess any delamination or whitening.

Spills and overflows need their own plan. When tank liquid overflows, part of the grating sees high-concentration acid and can be damaged within a short time even if it is normally resistant. Keep neutralising and rinsing materials ready rather than waiting for discolouration.

What to put in the inquiry

State the medium, concentration, temperature, contact mode, cleaning frequency and rinse water quality; contact mode should distinguish splash, immersion and acid mist. A request for acid-resistant grating is not enough to select from.

Also give span, support arrangement, load requirement, slip class, colour and fire requirement. If the plating shop has conductivity or static requirements, say so as well, because ordinary FRP grating does not conduct.

• Medium, concentration and temperature are all required.
• Check span, supports and load against the real equipment.
• Edge seal material must suit the resin system.
• Confirm fire and antistatic requirements separately.

Delivery documents should cover resin type, surface veil, fire rating and edge seal material. Where traceability is required, add batch and raw-material certificates. To check the approach against other sectors, see FRP grating applications by industry