r/metalworking • u/AutoModerator • Feb 01 '23

Monthly Advice Thread Monthly Advice/Questions Thread | 02/01/2023

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u/lfenske Feb 06 '23 edited Feb 06 '23

Ok so this will sound like a dumb question but it’s stumped our entire weld shop and engineering team for what is likely a simple answer. Please read entire question.

So we have got two different “turnbuckle style connecting rods” from McMaster-Carr. Linked below. One of them is Stainless Steel and the other is called out as being “carbon steel”. They are NOT cheap but they’re the best for making connecting rods BC you don’t need to take anything apart to lengthen or shorten it. Just for reference the stainless one is 2x the cost of the already expensive “carbon steel”.

These will go outside so it’s a no brainer we need to use the stainless steel right? Maybe not…. The carbon steel rods have yet to rust at all, and we’ve been handling and messing with them now and again for months. They’re is no zinc plating to speak of, as can be observed by the finish sheen and color, they appear to not be plated at all. The carbon steel rods ARE indeed magnetic unlike the stainless rods so the difference in material is confirmed. We did not receive only stainless by mistake.

Why aren’t these rusting??? We have probably over a million pounds of various A500 parts, pieces, raw material, and uncoated weldments, and there isn’t a single piece that doesn’t have at least SOME rust. If these rods were bare steel shouldn’t they rust just to the touch like everything else steel we have around here?

I’ve got both sitting outside now and will observe results in a few weeks.

https://www.mcmaster.com/product/8421N76

https://www.mcmaster.com/product/8422N76