Stainless Steel Fabrication and Supply in Richmond, VA

The dividing line is chlorides and aggressive chemistry. 304 is fine for general atmospheric exposure, mild chemicals and structural stainless, and it is meaningfully cheaper. The moment your part contacts chloride-bearing solutions, brackish or coastal moisture, or warm acidic process streams, you need 316L because its 2 to 3 percent molybdenum resists the pitting and crevice corrosion that destroys 304. In Richmond's chemical-processing applications, fabricators often default to 316L for anything wetted because the cost difference is small relative to the consequences of a corroded process line. The low-carbon designation also matters for welded assemblies: the L grade resists sensitization at the weld, which is where 304 commonly fails first. If you are unsure of the exact chemistry, err toward 316L for wetted parts and reserve 304 for dry, structural or mildly exposed components. Sending the corrodent, concentration and temperature with your RFQ lets the shop confirm the grade rather than guess.

Passivation restores the chromium-oxide film that gives stainless its corrosion resistance, a film that machining, grinding and welding disrupt while also smearing free iron from carbon-steel tooling onto the surface. Left untreated, that free iron rusts and can trigger localized corrosion on an otherwise sound stainless part, which is a frequent surprise for buyers who assumed stainless is automatically rust-proof. Passivation per ASTM A967, usually a nitric or citric acid bath, dissolves the free iron and re-forms the passive layer. It is not always included by default in a fabrication quote, especially from shops that also run carbon steel, so you should call it out explicitly in the PO for any chemical-processing or energy part. For welded assemblies, also confirm the shop pickled and passivated the weld zones, since heat tint from welding is itself a chromium-depleted region that corrodes if not removed. The cost is modest; the protection is essential.

17-4PH is a precipitation-hardening martensitic stainless that combines good corrosion resistance with high strength, which is why Richmond energy and defense work uses it for valve parts, shafts and fittings. Heat treated to the H900 condition it reaches around 190 ksi tensile and 170 ksi yield, far above what 304 or 316L can offer. Other aging conditions like H1025 or H1150 trade some strength for improved toughness and ductility, so the heat-treat condition is part of the spec, not an afterthought. Shops typically machine 17-4PH in the solution-annealed condition where it cuts similarly to a medium-carbon alloy steel, then age-harden it; for tight-tolerance parts they rough before aging and finish after, accounting for the small dimensional change that aging causes. Always specify the target condition (H900, H1025, etc.) on your drawing, because the same part in different conditions behaves very differently, and confirm whether heat treat is in-house or a subcontract step that adds lead time.

Only when the application genuinely demands it, but in those cases it is clearly worth it. Duplex 2205 has a mixed austenitic-ferritic microstructure that gives it roughly double the yield strength of 304 or 316L plus markedly better resistance to chloride stress-corrosion cracking, which is the failure mode that limits austenitic stainless in hot, chloride-rich service. For aggressive chemical-processing streams, brackish or seawater-adjacent energy applications, and high-pressure piping where wall thickness can be reduced thanks to the higher strength, Duplex pays for itself. The downsides are real: it costs more per pound than 316L, machines harder and slower, and demands careful welding procedure control to maintain the correct ferrite-austenite balance in the weld. For a routine wetted part that 316L handles, Duplex is overkill. Reserve it for the high-chloride, high-temperature or high-strength cases, send the service conditions to the shop, and let them confirm whether 316L will do or whether the upgrade is justified.

Stainless costs more on both fronts than carbon steel or aluminum. The austenitic grades 304 and 316L work-harden aggressively, so shops run slower speeds, sharper tooling and steady feeds to avoid glazing, which lengthens cycle time and increases tool wear, and that shows in the quote. Material itself runs several times the price of equivalent carbon steel, with 316L above 304 due to its molybdenum content and Duplex 2205 higher still. On lead time, common 304 and 316L sheet, plate and bar are well stocked by regional service centers, so standard sizes move quickly, but 17-4PH bar in specific diameters and Duplex 2205 plate can require longer sourcing if not in regional stock, so flag those grades early in the RFQ. Heat treat for 17-4PH and passivation for any wetted part are subcontract steps that add days each. The most reliable way to keep both cost and time in check is to specify the exact grade, condition, finish and any passivation or cert requirement up front so the shop quotes the real scope the first time.