Sandblasting Stainless Fasteners

[Chilliwack Murray]

Just wanted to double check something with some others.

Doing some overdue pool maintenance and I have a lot of SS pool equipment screws that are covered with rust from what they were touching. They are all different sizes and lengths so it’s a pain to find replacements.

They are stainless and not plated so I don’t see an issue giving them a quick pass in the blaster. I tried one and all the rust came off very easily.

Since it’s not a coating, I don’t see this impacting the corrosion resistance but always welcome a second opinion before its all underwater again.

 

[davewo]

You could blast them, but a little soak in vinegar will do the trick.

 

[zkling]

Keep in mind that a rough surface will rust easier than a smooth surface. AKA don't go with a very aggressive grit on the sand.

 

[Chilliwack Murray]

Right, hadn’t thought of that. Thanks.

 

[kkroger]

CLR from the store will wash the rust or even Muriatic Acid... Or Pickling Solution for passivating stainless welds... though that is a pretty spendy option. Unless you know someone who has it on hand.

 

[Chilliwack Murray]

CLR from the store will wash the rust or even Muriatic Acid... Or Pickling Solution for passivating stainless welds... though that is a pretty spendy option. Unless you know someone who has it on hand.

I tried CLR on the screws and all the plastic parts. Let it soak in, tried scrubbing, scrubbing with water and full strength.

Didn’t touch the rust at all. Zero. Nada. I’ve concluded it’s just snake oil unless someone can show me otherwise.

I needed to get it done and move on so everything got a quick pass with glass bead and looks good. Plastic and all.

 

[rlitman]

I would suggest never using muriatic acid on stainless. It can lead to worse rust in the future, or crevice corrosion cracking.

Citric acid is the best. I've had good luck using a mix of Barkeeper's Friend (oxalic acid) with Ospho (a phosphoric acid / detergent mix).

 

[rlitman]

I tried CLR on the screws and all the plastic parts. Let it soak in, tried scrubbing, scrubbing with water and full strength.

Didn’t touch the rust at all. Zero. Nada. I’ve concluded it’s just snake oil unless someone can show me otherwise.

I needed to get it done and move on so everything got a quick pass with glass bead and looks good. Plastic and all.

It's not snake oil, but it's very weak. Stronger than vinegar though. You could seal the fasteners in a zip-lock bag with CLR for a few weeks, but it's not going to work overnight unless you heat it. If you've got a side burner on your outdoor grill, you could boil a CLR solution in a scrap stainless pot, and cook your fasteners in that. That would work very well.

As pointed out above, the blasting is going to scar the surface, and with stainless, unless you remove ALL the corrosion, you'll still have active sites that will flash rust over quickly. That's why passivization is best.

Beyond that, the most I can say is that the chlorine in a pool is tough on stainless.

 

[Kev In]

I know little about stainless screws and rust. A possible solution would be a tumbler or vibrating parts tumbler.

 

[desertforge]

If your blast media has been used on regular steel then blasting will make it rust again. Blasting the rust may in fact drive tiny particles of rust or iron into the surface. The main thing is to get the surface free of iron. Stainless is only stainless by virtue of a surface layer of chromium oxide. Any iron oxide (rust) or free iron is trouble. Blasting is fine but it doesn't passivate. You need the acid preparation or electro polishing to be sure.

 

[Chilliwack Murray]

Thanks, that’s some useful information. The media is not brand new but has been used very, very little so hopefully contamination.

The hardware has been submerged for some time now and no signs of rust but I’ll watch for any as time goes on. I didn’t have a ready source for replacement in the short window I had to reinstall everything or I would have just got new.

Question on the oxide coating, will it develop underwater or does it need to be exposed to air? It may have been better to let them sit before installing but again, I didn’t have time.

 

[racingtadpole]

The reaction is driven by oxygen, present in both air and water

 

[Strouty]

If your blast media has been used on regular steel then blasting will make it rust again. Blasting the rust may in fact drive tiny particles of rust or iron into the surface. The main thing is to get the surface free of iron. Stainless is only stainless by virtue of a surface layer of chromium oxide. Any iron oxide (rust) or free iron is trouble. Blasting is fine but it doesn't passivate. You need the acid preparation or electro polishing to be sure.

This was my first thought, but I have no experience. Have you tried evaporust or something equivalent?

 

[rlitman]

...Question on the oxide coating, will it develop underwater or does it need to be exposed to air? It may have been better to let them sit before installing but again, I didn’t have time.

So long as the water is oxygenated, it will develop just fine under water. Even under salt water. In crevices and in places out of the reach of oxygen, you may get into trouble. This is particularly an issue with threads inside fasteners under salt water.