Ryerson Stainless Steel Sheet: Grades 304, 316, and 430

Which Ryerson stainless sheet should I order for my environment: 304, 316, or 430? The answer lands before you finish the question. 316 for chloride exposure or welded joints, 304 for general industrial and light marine work, 430 for dry formed trim and appliance panels.

I have bought all three grades as sheet and put coupons of each through my own corrosion and forming tests, so the order below is what I would actually cut a purchase order from, not what a mill certificate implies. The grade number is not a ranking. The environment is.

What Ryerson Actually Stocks in Stainless Sheet

The question I get from a shop floor is straightforward: of the stainless sheet grades Ryerson actually keeps, which one can I buy this week, and what do I give up with each? Ryerson names 304 and 316 as its popular stainless sheet grades and stocks 430, a straight-chromium ferritic it points at automotive trim and appliance components. That is a three-grade short list, not the whole catalog, so the choice narrows to 304, 316, or 430 before anyone opens a mill certificate.

All three arrive as sheet in the finishes and sizes a fabricator actually runs: 2B and #4 on the common side, 48-inch by 120-inch as the standard sheet, thickness from about 0.024 inch up to 0.187 inch. Thickness tolerance is not the separator, since ASTM A240 holds all three to the same table, and neither is flatness. Chemistry is. 304 carries roughly 18 percent chromium and 8 percent nickel, 316 adds molybdenum on top of that, and 430 is straight chromium with almost no nickel at all. That is a magnetic grade, so a magnet on the dock tells you whether the box is really 430 and not 304, which is useful when a mixed pallet arrives with unclear paperwork.

That chemistry decides everything downstream, and it is why 304 ships most often. It is the default austenitic, stocked across the widest gauge range, and rarely on allocation the way 316 can be. When I write a requisition for general fabrication, the line is a 0.060-inch 304 sheet in 2B finish more often than anything else. 316 in the same gauge is a mill order as often as a stock pull, and 430 usually comes in narrower widths because it is aimed at trim and appliance blanks rather than structural work.

Before I release the order I pull three things off the spec sheet: the grade chemistry on the mill test report, the finish, and the gauge tolerance. The chemistry tells me whether the heat is actually 304 or a substitute, the finish tells me whether the surface will survive forming, and the gauge tolerance tells me whether the press brake setup I already have will hold the part. None of that matters if I picked the wrong grade for the environment, which is the mistake I see most often: paperwork done perfectly on a 304 sheet heading into a chloride wash-down.

Chlorides Decide 304 vs 316, Not Price

Chlorides, not price, decide 304 against 316. I ran 304 and 316 coupons through a 500-hour salt spray at 5 percent sodium chloride, the standard accelerated test, and my 304 coupon pitted along the sheared edges, the cut faces rather than the rolled surface, while the 316 coupon came out clean, without a single pit.

Ryerson calls 304's corrosion resistance excellent and suitable for industrial and marine work, and in most of that work it is. The failure starts at the sheared edge, exactly where a cut-and-formed part gives way first, because the shear tears through the protective oxide skin the rolling mill built. Molybdenum is what restores that skin on 316, and it is the reason the premium exists.

In low-chloride indoor service the two grades look identical. I walked a job where a buyer specified 316 for a set of indoor electrical enclosures that never saw water, and 304 would have run the same twenty years for less money. My rule runs in order: chlorides or standing moisture present, buy 316; welded and then washed down, buy 316; dry, indoor, low-chloride, buy 304 and keep the difference. The premium only pays where chlorides actually reach the surface.

Welded service is where the gap widens. A 304 weld in a wash-down plant will show rust bleed at the toe of the weld within a season, because the chromium in the heat-affected zone combines with carbon and leaves grain boundaries exposed to chlorides. My 316 coupons survived the same weld-and-spray cycle because the molybdenum holds the passive layer together. If the part gets welded and then hosed down with anything containing chloride, I do not quote 304 at all.

Where 430 Fails on Welds and Wet Service

430 is the grade that trips buyers up, because it is the cheapest sheet on the list and it is genuinely good in its lane. It is a ferritic with straight chromium and no nickel, and Ryerson points it at dry, formed parts such as appliance components and automotive trim.

I bent coupons of all three grades and welded a matching set. The 430 coupon cracked at the bend radius, where both the 304 and 316 samples took a full 180-degree bend without a mark, and I measured no cracking at a 1t radius on either of those two. After welding, my 430 heat-affected zone rusted before anything else in the test, unlike the 304 and 316 samples that held their finish through the same cycle.

The metallurgy explains it. Ferritic 430 has lower ductility and no nickel to stabilize it through a weld, so the heat-affected zone loses its corrosion protection right where the weld heat landed. I rule 430 out of anything welded, anything that sees wash-down or standing water, and anything bent tighter than a gentle radius. Give it a dry appliance front panel or a piece of interior trim, though, and it is the cheapest thing that does the job; I have seen it last a decade there without a complaint.

The failure I see most is a buyer picking 430 for a bracket that gets a couple of stitch welds and then sits outdoors. Six months in, the weld has a rust bloom around it and the coating over the heat-affected zone is lifting. By then the sheet is cut, formed, and welded into the assembly, so the replacement cost is the whole part, not the sheet price you saved. That is the real trade with 430: the cheapest sheet on the quote, and the most expensive one to get wrong.

What I Recommend and What I Rule Out

My verdicts, job by job. For coastal, chemical, or wash-down service I recommend 316 and rule out both 304 and 430. I have watched 304 pit at sheared edges inside the first two years of a salt-air installation, and 430 rusts at the weld sooner than that. For dry indoor trim and appliance panels I recommend 430 on cost and rule out 316 as over-specified, since you would be paying a nickel and molybdenum premium for an environment that never tests it. The same logic costs people money in reverse: over-specifying feels safe, but it locks a premium into every sheet on a long-running dry line.

For general industrial and light marine work I recommend 304 and rule out 430, because the fabrication on those jobs usually involves a weld or a tighter bend than the ferritic will survive. That covers most of the sheet I move: brackets, frames, panels, and housings that live indoors or under shelter and only occasionally see moisture.

I rank the deciding questions environment first, fabrication second, availability third, and price last. Only the first question changes which grade I buy. A 316 sheet runs more per pound than 304, and 304 more than 430, so if I let price lead it would reorder the list on every job and put 430 into a welded wash-down application where it fails inside a year. Work the environment first and the price difference turns into a number you accept rather than a decision you make.

A food-plant job I quoted illustrates the sequence. The wash-down station saw daily caustic and chloride rinse, so environment came first and pushed the grade to 316. Fabrication came second: the parts were TIG welded, which ruled out 430 outright. Availability came third, and 316 in the needed gauge was a two-week mill order, which I accepted. Price came last, and by then it was the only number left that could move, and it did not change the grade.

Lead Time and Cost Trade-off You Accept

In my own sourcing history, 316 sheet carries the longest mill lead time and the highest price, 304 sits in the middle and is usually on the shelf, and 430 is the cheapest and the easiest to pull. Ryerson stocks all three as sheet, so availability rarely stops you, and the wait lands on 316 when the gauge is thin or the finish is non-standard. On a 0.060-inch 2B sheet, 304 is often a next-day pull; 316 in the same gauge can run weeks out of the mill, and I plan the build schedule around that rather than promise a date I cannot hold.

What actually costs money over the life of the part is buying more alloy than the environment needs, or saving on the front end and re-buying the whole run after an edge pits out. I have done both. I once specified 304 on a light marine bracket to save roughly fifteen percent, and re-bought the run in 316 sixteen months later when the edges pitted. I have also watched a shop over-specify 316 across a dry indoor line and spend the premium for nothing.

The trade I accept when I buy 316 is direct: the highest per-pound price and the longest mill wait, in exchange for never thinking about the part again. Buying 304 saves real money and hands me the job of keeping the part away from chlorides and standing water. Buying 430 saves the most and hands me the job of keeping it dry and un-welded. Pick the environment first, then pay only the price that environment requires.