ZebraPaste

Ok pretty deep in the rabbit hole now. It seems we can swap the chromium oxide for zirconium hydroxide in the phosphate binder. This is currently being tested for ablative shielding on space shuttles and hypersonic vehicles. I’ll be ordering some to test shortly. Supposedly it’s rated for 2500C and is flux resistant. Borax will not win this.

Important Update….Lee you were very much correct to say don’t mess with the chrome compounds. Apparently adding the chromia (Cr2O3) is great for a reducing environment, it’s the best binder and adhesive available for a lot of industrial settings, but in an oxidizing environment in a temperature range that includes the warming phase of gas forges, it can transform into pure solid hexavalent chromium. So I will still be performing my tests just because I have the safety equipment to do so, but definitely don’t try to replicate it without really understanding the hazard it presents. It will basically turn your forging area into a superfund site after it kills you. It’s far worse than welding stainless and huffing the fumes for a week straight through a straw, it’s as bad an idea as you can possibly have. Mods or admin if there is any way you can delete the last post I made just in case someone reads it and doesn’t see this one I’d appreciate it. This is not suitable for anyone outside of a lab or very specialized industrial uses. Will update with test results. Maybe even a picture. sorry about that

Just out of curiosity I do feel the need to mess with the chrome oxides haha. As I read more though it’s very important not to have it in a mix containing any calcium material. Turns out at medium temperatures (right around forging and welding temperature) it converts to hexavalent chromium. I’ve ordered some chromium trioxide to experiment with, I’ll be using a zero contact safety procedure. I refuse to accept that the inside of my forge is a consumable material. what is your background if I may ask? You seem educated not just like someone who reads on these subjects.

Hi Lee, I continued my post in another thread under the everything else category. One test I did with the aluminum phosphate binder went very well. I’m attributing it to having a contamination of about .25% hydrated calcium aluminate cement. My mixture was zircopax frit…I fired a mix of zircopax and sodium meta silicate to white hot and smashed it up through a screen until nothing was larger than 1/16”, a small amount of coal slag, perlite that I ground into the mix, and some alumina. Exact measurements I’m not sure about but call it 75% zircopax total. Turned out very hard and thermal shock resistant. Now I’m reading that to get real flux resistance from borax products I need to add chromium oxide since everything else either melts with it at low temps or gets stress cracks from it.

Hi all sorry I should’ve included some safety precautions. The acid I bought for my experiments was 85%, it will blind you if it gets in your eyes so goggles are a good idea. If you get it on your skin, or at least on mine, it will itch until you clean it off, probably end up with a chemical burn if you don’t clean it so gloves aren’t a bad idea either. Stirring with a glass rod is recommended. Stainless rod is probably not going to hurt it but might discolor a bit from dissolved iron. Also at elevated temperatures the acid will attack (very slowly but still needs to be considered) almost any container you have. Use a borosilicate glass if you can that will let you use a small torch or even a candle to keep it heated. I used a torch, worked good just have to keep an eye on it and have some patience, don’t over heat it. Also tried in an air fryer/ small convection oven. It worked but dries out the surface and has to be stopped and stirred, it’s not a great way to do it but will work if you need it to. The weather (and work schedule) has kept me away from this for a bit but once I get back to it I have another mix to try. It’s a promising one for the floor/flame face, very hard and abrasion resistant. thanks for reading

Update to the aluminum phosphate binder. One test (filled a steel bottle cap) turned out successful. No shrinkage cracks, thermal shock test passed, harder than expected (used it like a sharpening stone on a scalpel I made from L6 scrap). Can’t get it work work again, must have some contamination or something.

A little late but maybe this will help someone. Galvanized coating is not just zinc. It’s mostly zinc, but also has more than a small amount of lead, antimony, cadmium depending on what process was used and the grade of coating. The zinc is the least of your worries. I’ve had galv poisoning a few times, sucks each time and you don’t get immune to it it actually gets worse each go around if the dose/exposure duration is the same. Anyway there’s a chelating chemical called EDTA disodium-calcium that you can get online. It’s very important to understand the caution you need when using that, it will strip metal ions from your body, starting with the heaviest (lead etc.) and moving all the way to down the line. If you use it too much it will make you anemic and hurt you. It’s an old treatment for chemo detox and regular heavy metal poisoning. It’s been replaced with other things for human use but it’s cheap and shelf stable so if you’re in a pinch and idk swallow some mercury it’ll do the trick. Read about it thoroughly before you use it.

I’ve gotten my hands on some phosphoric acid and aluminum hydroxide. Mixing them with a little water (amount almost doesn’t matter it acts as a vehicle/lubricant for the reaction) and gentle heating (keep above 170F but below 212F, it will boil but not at true water boiling temp) makes aluminum phosphate. If you heat too much you will get crystalline product at the bottom of your container, I used a mason jar and burnzomatic. There are plenty of videos on the process online. I’ve tested some aggregate mixtures and curing temperatures. This stuff is amazing so far. The mixture doesn’t dry and harden at room temp, which means you have loads of time to work it into your shape/on you the surface required. Curing is starting around 175F which is lower than what google showed in search results. Very hard and durable product at 400F cure, better than any water cure castable I’ve gotten yet. It is cheap, and quite strong as far as binders go. You won’t need 85% lab grade acid, you can boil down cola if you really wanted to. So far any aggregate has responded well, but mixing with a water curing cement has yielded significant expansion. The expansion is temperature dependent and increases in a linear fashion. Curing at 180F gives roughly 35% increase in volume, 400F about doubles the initial volume. The product is well worth the expense of raw materials. If you’re looking to create your own firebrick this is very good for making an insulation layer and flame face/abrasion resistant face all in the same unit. My tests are showing virtually no cracking when heated with propane air. Will use acetylene/oxy to failure for more data.

Excellent advice rockstar.esq and Brian Hibbert. It is very often the job you take that hurts the most. Economy of scale is also very important. We are a small fabrication shop that specializes in stairs and rails. On occasion we get asked for structural steel but often we turn the customer to other shops because we know right off our bid won’t be competitive or it won’t be profitable for us. Learned that the hard way so being cautious and not over extending yourself is very important. One thing I’d like to add is know your market in your area. We’re right next to the very wealthy towns and New York, often we see oh they are willing to pay $90k for this house to have metal work….9 months later the project is done and our profit is nonexistent. So don’t be swayed by a contractor being willing to share a budget number with you.

Has anyone here tried making crucible steel in a propane forge? I’ve seen many videos of using coal set ups and even one guy on YouTube (shake the earth, his videos are cool) using a microwave casting set up. I’m making my forge to be able to take the heat and will try it anyway but if anyone else has I’d like to hear their side of it. Thanks

Hi JHCC, I want the cast mixture to be more durable and already have the IR reflective properties of the available coatings. I have been experimenting with binders, instead of silicate binder or calcium aluminate, the next one I’ll be trying is alumina phosphate. Even if none of this works it’s still very fun.

I’m currently exploring how to get better performance from cast refractory. Some notable things I’ve come across include calcining your own additives. I learned that if you burn epsom salt with a torch it releases some toxic gas that is basically sulphuric acid. What’s left over however is magnesium oxide, the highest melting temp oxide you can get. In small amounts it increases the melting point of refractory materials. 1/10% is enough to stabilize alumina and zirconia when brought up to full temp (3000f+) Alumina hydroxide aka alumina hydrate is usually available as a pottery additive. If you calcine/burn the heck out of it you get alumina as a raw material. Great for refractory mixes. Don’t mix alumina hydrate into refractory mixes. It has made several of my tests fail. The hydrate vents a ton of water (roughly 1/3 by weight) when it heats up and it blows up and or crumbles to dust. A fair few times I’ve read posts on websites about people trying to create a flame face coating using water glass/sodium silicate and a product called zircopax. The zircopax is never going to stick doing that, and due to the super fine particle size it will flake and crack and warp as it dries. Get calcium aluminate cement binder instead. When using the CAC, calculate the amount of water you need, and use the water glass instead of just water. Water glass is 40% solids, so that remaining 60% is available water for your cement to cure. The effect is a faster cure, and a much stronger binder. Sodium metasilicate is sold dry as deck cleaner. It’s cheaper than buying the pre diluted solution, just dissolve it in hot water. If youre trying to go the zircopax route like I am since its got a higher service temp than most other products, you will benefit from making frit out of it first. Mix a batch with 10% water glass and pack it into a sheet. Let it dry and then heat it up as much as you can. I ran it in my forge until it was white hot. Then smash it up into coarse sand size particles. Mix 4 parts sand size particles, one part fine particle as you bought it (should be 2-5 micron powder), and somewhere around 15% by weight of CAC. Casting this 1/2” thick should be a very durable material. As an optional note I got from one of the manufacturers of similar products, add a 1/4% by weight polyester fiber to the mix. Its job is to burn out and make vents for excess water vapor to get out as you cure and fire the mixture.

When we have rails or other steel products going outside we use cold galvanizing paint as the primer coat. We have to warranty our stuff so we opt for the zrc brand 98% zinc. It’s certified for repair on hot dipped industrial products. Doesn’t have the same abrasion resistance as hot dipped but it’s as protective as it gets and takes top coat really well. Best brand of paint we’ve used is majic farm implement paint. Not sure if those are available where anyone else is but I’d put those layers up against sand blasted and powder coated products any day.

I never spoke directly with Frosty but his posts and replies were what drew me to this forum. Literally his opinion on what we’re doing now was the only reason I made a profile. You are missed Frosty.

Update to coal slag puck: calling this one a failure. Didn’t break from the thermal shock testing but lost strength and I broke it with a slight smack from a steel bar. Next puck will use phosphate bonded alumina binder.