Picking a metal for your part

Side by side

Strength numbers are supplier figures for one temper or grade. Your part's drawing or engineer has the final say.

304 vs 316 stainless

• The difference: 316 adds 2 to 3% molybdenum. That fights pitting from chlorides.
• Pick 316 for: ocean spray, boat hardware, pool and hot tub fittings, and parts in de-icing salt all winter
• Price: one Canadian supplier sells a small flat bar for $26.11 in 304 and $33.09 in 316
• That's about 27% more for 316
• Machining: one rating scale puts 304 at 45% and 316 at 40%, against 1212 steel at 100%

Aluminum vs steel

• Aluminum weighs about a third as much as steel for the same size part
• 6061-T6 aluminum yields at 275.8 MPa typical. Canadian 44W steel yields at 300 MPa minimum.
• Mild steel needs paint or plating outside. Metal Supermarkets rates 6061's corrosion resistance as good.

6061 vs 7075 aluminum

• 7075-T6 yields at 503.3 MPa typical, near double 6061-T6
• 6061 is excellent for welding and good for machining, says Metal Supermarkets
• 7075 is not recommended for welding because of cracking risk
• 6061 shows up in frames, structural parts, machined parts and welded assemblies
• 7075 is used in aircraft parts where strength for the weight matters

Mild steel

• Low carbon steel, with 0.05% to 0.3% carbon
• It rusts unless it's painted, plated or galvanized
• Canada's common structural grade is CSA G40.21 44W, with a 300 MPa minimum yield
• It machines easier than stainless: 1018 steel rates 78% on the same scale where 304 rates 45%

What metal costs

One Ontario supplier's list, October 2026, material only, before tax:

• Mild steel sheet and plate: about .80 a pound
• Stainless sheet: about .30 a pound
• Aluminum plate: about .91 a pound

Material is only part of a quote. Setup, machine time and finishing make up the rest.

Quick picks

• Outside near salt: 316 stainless
• Light and welded: 6061 aluminum
• Light and very strong, not welded: 7075 aluminum
• Strong and low cost, painted: mild steel
• Not sure? Tell the shop what the part does. They'll suggest a metal.

Sources

• Metals 'R' Us: 304 vs 316, stainless buying guide and steel grades
• Hill Industrial Tools machinability ratings
• Superior Metals and Alloys on aluminum
• United Aluminum alloy data
• Metal Supermarkets: 6061, 7075, aluminum grades and round bar uses
• Online Metals: 304 stainless
• Steady Steel material prices, Newmarket ON
• Metal Supermarkets: mild steel and steel vs stainless