Many PV power station operators find yellowish-brown flash rust appears on new stainless bolts several months after installation. Buyers often mistake it for inferior stainless material. In fact, most flash rust comes from transportation dust and iron debris generated during installation. Passivation treatment directly determines salt mist resistance. Different standards should be adopted for inland PV stations and tidal flat projects within 5km coastline.
| Surface Treatment | Neutral Salt Spray Duration | Flash Rust Resistance | Suitable PV Scenario | Notes |
| Pickled raw finish (without passivation) | 200~350h | Poor, prone to surface flash rust | Inland mountain distributed PV far from coastline | Forbidden for coastal tidal flat projects |
| Pickling + standard passivation | 500~800h | Good, stable oxide protective film formed | Riverside, inland lake and mild coastal PV stations | Mainstream solution with best cost performance |
| Pickling + enhanced sealing passivation | Over 1000h | Excellent, block chloride penetration | Tidal flat within 3km coastline, nearshore PV projects | Higher cost, first choice for offshore floating PV |
1. Inland mountain PV: SUS304 bolts with standard pickling passivation to meet 25-year design life; 2. Lakeside & riverside PV stations: SUS304 passivated fasteners are mandatory to reduce corrosion risk in rainy seasons; 3. Tidal flat PV within 0~5km coastline: Upgrade to SUS316 bolts with sealing passivation to resist continuous chloride erosion from sea wind; 4. Offshore floating PV: Full SUS316 bolts with enhanced sealing passivation matched with PTFE insulating gaskets to block galvanic corrosion.
1. Light yellow flash rust: Wipe with dedicated stainless rust removal & passivation cleaner, rinse and dry; bolt replacement unnecessary; 2. Pitted corrosion pits: Passivation film damaged, corrosion will expand gradually, batch replacement is recommended; 3. Prevention: Avoid carbon steel grinding debris sticking to stainless bolts during construction, clean surface dust after installation.