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I plan on building a power rack for my home gym and was wondering what kind of metal/coating I should use when building it since it will be stored outdoors. Most commercial power racks are built using mild steel and are coated with paint to protect it from rust. These racks should last when used indoors but I'm not so sure if it will when it is kept outdoors.

If I were to build my power rack from mild steel, how should I go about protecting it from rusting? While the rack will stay outdoors, it will be situated under some kind of shade/tent similar to this:

tent

The power rack will stand over concrete or plywood (over concrete), not grass/soil.

With these details in mind, can anyone suggest how I should treat/coat the mild steel? I've taught of powder coating it but again, I'm not sure how that would hold up. How about chroming? Is it too expensive/overkill?

How about using something similar to the following:

These are pictures of my old bench. Since the bench is still standing strong after so many years, I take something like its material would be appropriate for my use case. What do you call this kind of metal/coating, anyway? What properties does it have and is it difficult or expensive to produce/replicate?

Please provide details as to why I should prefer each method over the other. If you would prefer to use some other kind of metal(stainless steel, galvanized steel, aluminum etc), please state why. I tried Google-ing the pros and cons of each method of coating I stated above but I'm still unable to reason out to myself which one to use. If all of them would equally serve the purpose, I guess it will all boil down to which one is the most cost-effective to produce.

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If you're wondering why I'm building my own power rack instead of buying one, it's because none are being sold in my area/country. –  Victor Nov 13 '13 at 18:12
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I'd be worried about the insides of the tubes rusting - even if you have a shelter above it, condensation or blowing rain may get your rack wet. For my steel frame bicycle, I used a framesaver oil spray to help protect it from water (engine fogging oil might be easier for you to find). Maybe you can use something like that to make sure the insides of the tubes are protected. –  Johnny Nov 13 '13 at 18:31
    
If I were to paint the outside of the tubes, will I apply this oil on the outside too (I'm guessing there's no need for it)? Also, how long do these products last? The tubes will at least be 8 feet so reapplying them might become a hassle if it is going to be done very regularly. –  Victor Nov 14 '13 at 0:33
    
Just the inside of the tubes, no reason to apply on top of paint (and the oil dries to a somewhat sticky consistency that is hard to wash off so you won't want it on any exposed surfaces where it may get on your skin or clothes). As long as it doesn't wear off because tubes regularly slide together, it should last for years - I treated my bike frame several years ago and the coating still seems good. –  Johnny Nov 14 '13 at 1:40
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2 Answers

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Normally gym equipment is powder-coated. in your picture, they have used an electrostatic powder coating process and finished with a sort of hammertone finish..

IMO- your options are as follows:

  • Stainless steel is the best metal in terms of durability. it will never rust, however, its more expensive and is slightly harder to drill/bend. I would recommend pricing the bench with Stainless, then you can assess the viability. In terms of stainless, the most common stainless is 304, which is industry grade.. This grade is perfect... but will turn slightly yellow over time, if you are concerned with tarnished stainless you can go for the more expensive 316 stainless.
  • Mild Steel is your other option, and obviously this will rust, so your rust prevention options are

    • Metal Oxide primer with enamel coating (paint)... which will not look as clean and will rust after a short time
    • Powder coating - you can imagine this as a sort of plastic coating which is baked onto the metal. in terms of finishes. this looks really neat, however the impact of the power bar on the bench will chip away the coating and it will show signs of rust after a while. not to mention that the coating is only on the outside of the tubing and the tubing will rust on the inside.
    • Chrome is another option, in which the metal is coated in chrome, this is also on the exterior of the metal, but I am not too certain if you will find a person who can chrome such a large item

    • Your last option (and most cost effective) is to galvanize the metal. this results in a zinc layer being coated on all surfaces of the metal (inside and outside) your second photo looks like it has been hot-dipped galvanized. the galvanizing will look really shiny at first, but will form a dulled coating and will last for many years.. Galvanizing comes in two types

      • Hot dipped , where your bench will be dropped into molten zinc and will come out with a thick layer of zinc covering all surfaces. with this your bench will last for 20+ years without rusting.
      • electrogalvanized, where the bench is dipped into a solution and a current creates a charge which attracts the zinc coating (this coating is a lot thinner so will not last as long), however the finish is a lot prettier. I would not recommend this in your case.

So to summarize, I would say your options are stainless steel, or hot-dipped galvanized steel. Both will be extremely durable but I like the look of stainless more

If you decide on Galvanized, I would also place some rubber strips in the areas where the power-bar lands on the bench, since the zinc coating will wear away there over time.

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Just to clarify, I'm building a power rack and not a bench. I just took a picture of the bench to show the type of finish and ask about it. Here's a picture of what I'm trying to build. Bodybuilder not included. –  Victor Nov 14 '13 at 0:58
    
Main problem with stainless steel is that it really is more expensive, not just by a tad. Not to mention it is difficult to find a 3mm thick rectangular SS tube in my area. Since stainless steel is much stronger than mild steel, I could probably get something thinner without risking buckling or some kind of deformation. How much thinner, I'm not sure. Knowledge with tensile strength numbers might be needed to figure this one out. –  Victor Nov 14 '13 at 1:08
    
Another problem with stainless steel is that its yield strength to tensile strength ratio is very low compared to mild steel. So while SS can take more load before ultimately breaking, it will deform permanently much more faster/easier compared to mild steel. It is for this reason that gym equipment are usually built with MS (aside from the cost-effectiveness factor). I believe that is also why in structural design, yield strength is more of the limiting factor than tensile strength. –  Victor Nov 14 '13 at 1:12
    
also, the galvanized coating will reduce the hole size of your adjustment holes. so the tolerances need to be extended. –  Hightower Nov 14 '13 at 6:29
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At the end of the day the thicker your material, the longer it will last in terms of rust. Metal oxide primer with an enamel coating will last. but you will be guaranteed to have rust where moisture can sit (this is near joints, inside the tubing, or on flat surfaces) and in areas where you chip the paint. If your tubing is allowed to fill with water, it will rust in no time. If you are near the coast, rust will be faster. with that in mind, I do pool fencing which, lasts 30years with paint.. There is no contest wrt galvanizing however it will not rust and will be maintenance free for 30yrs + –  Hightower Nov 19 '13 at 21:08
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The finish shown is a type of paint - "Hammerite" is either the name, or the brand name of the most popular/first version. It's presumably on mild steel. However, any automotive paint should work (think about it) - and COULD be cheap if you have a cooperative paint shop and you don't care what color it is (ie, they can spray some excess when they spray something else, so it's not a special job where they have to mix paint and clean the spray guns just for your tiny job.) Some shops will, some shops won't - all you can do is ask.

Chrome is probably a bad idea - it's relatively expensive and the electro-plating process can increase the odds of steel cracking from hydrogen embrittlement.

Hot dip galvanizing (zinc coating) is probably a good option if you can find a shop with a tank big enough - ask around for places that do boat trailers - covers inside and out (be sure to put in holes so it can drain out, or you'll get a tubeful of zinc and a larger than expected bill for the coating process), and is durable in weather. It only comes in one color, which changes over time from shiny silver to a dull gray. It is preferable to using galvanized steel stock to build from, because you coat the whole object after fabrication, so the welded joints are protected.

Powder coating should work fine. It may chip a bit on the top section where the weight bar sits. It comes in many colors, and is fairly tough as compared to most paints - but hard to repair if it does chip.

By far the most cost effective method usually is to do through cleaning and preparation (the key to ANY paint job lasting) and paint it yourself, using a primer for steel (zinc chromate primer, for instance) and a topcoat - then keep an eye on it and sand and repaint whenever you see signs of new rust. You could use either the mentioned oil coating or an automotive undercoating on the inside of the tubes if feeling particularly cautious.

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What's your take on Johnny's comment on my question? Is it possible to coat the insides with paint too or should I use some oil to coat the insides like he suggested? –  Victor Nov 14 '13 at 0:28
    
As per Hightower's answer and further googling, hammertone is the type of finish, Hammerite is the brand of paint. –  Victor Nov 14 '13 at 0:37
    
It would be hard to get paint to apply evenly throughout the inside of the tubes, the nice thing about the oil is that when it touches the surface, it spreads out to coat evenly. But the longest tube on my bike frame is less than 3 feet long, so I'm not sure how well it will spread through an 8 foot tube. Hot dip zinc sounds like the best way to make sure the tubes are protected inside and out. –  Johnny Nov 14 '13 at 1:42
    
Either should work, if done carefully. Hot dip galvanize is probably the best, but oil, undercoating or paint are probably all more than adequate for the insides of the tubes so long as you put enough in and rotate things around enough to get good coverage. Really it's doubtful if anything is needed - Plenty of swingset, motorcycle and bicycle frames don't appear to have anything done to the insides and last decades in the weather anyway... –  Ecnerwal Nov 14 '13 at 2:44
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