Exhaust, Removing Aluminized Coating

[Bob Holmes]

I could have sworn that I'd read a post, here, about dipping the ends of exhaust pipe in something to remove the aluminized coating.

I need to do some exhaust work on the Red Furd and I don't like to grind the stuff off, it still seems to contaminate the weld and it thins the tubing where I want to weld.

Any help in either finding the post or providing the solutino would be appreciated.

[milner351]

phosphoric acid, or muriatic? (hydrochloric)

Phosphoric acid may be used as a "rust converter", by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-brown iron(III) oxide, Fe2O3 (rust) to black ferric phosphate, FePO4.

"Rust converter" is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called naval jelly. It is sometimes sold under other names, such as "rust remover" or "rust killer". As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.

After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance (such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes).


Hydrochloric acid is a strong inorganic acid that is used in many industrial processes. The application often determines the required product quality.[5]

Pickling of steelOne of the most important applications of hydrochloric acid is in the pickling of steel, to remove rust or iron oxide scale from iron or steel before subsequent processing, such as extrusion, rolling, galvanizing, and other techniques.[5][17] Technical quality HCl at typically 18% concentration is the most commonly used pickling agent for the pickling of carbon steel grades.

Fe2O3 + Fe + 6 HCl → 3 FeCl2 + 3 H2O
The spent acid has long been re-used as iron(II) chloride (also known as ferrous chloride) solutions, but high heavy-metal levels in the pickling liquor have decreased this practice.

The steel pickling industry has developed hydrochloric acid regeneration processes, such as the spray roaster or the fluidized bed HCl regeneration process, which allow the recovery of HCl from spent pickling liquor. The most common regeneration process is the pyrohydrolysis process, applying the following formula:[5]

4 FeCl2 + 4 H2O + O2 → 8 HCl+ 2 Fe2O3
By recuperation of the spent acid, a closed acid loop is established.[17] The iron(III) oxide by-product of the regeneration process is valuable, used in a variety of secondary industries

[TC]

Why would you use a Grinder??.........You could user a DA and a semi-coarse sanding disk.............Or even a real stiff wire brush chucked in a high speed drill/grinder would probably work.......

[Bob Holmes]

I use a flap wheel on a "grinder." My bad, should have been more specific about the abrasive.

[TC]

I use a flap wheel on a "grinder." My bad, should have been more specific about the abrasive.

Have you tried using a Fiber sanding disc, like these........The coarse one should do the job......

[Bob Holmes]

Funny, I've got a set of those, never thought to use them. Thanks.

[CDMBill]

Bob, I have used the flap disk and the fiber disks with good results. Did my whole system that way.

[Bob Holmes]

Nice

[SuperBuickGuy]

Have you tried just burning it off with a MIG when you weld it together (do wear leathers - bet that stuff splatters).

[Bob Holmes]

I just dont' like contaminated welds.

[Beagle]

can you clamp a (-) battery charger to the exhaust part, (+) to a sacrificial anode, dip just the end of it in baking soda and water mix? Cathode / electrolysis?

If anode / anodizing aluminum is an additive process, then using it as the cathode should cause removal? Just thinking out of my butt here, don't flame my pathetic attempt at mr. science...

[STINEY]

can you clamp a (-) battery charger to the exhaust part, (+) to a sacrificial anode, dip just the end of it in WASH soda and water mix? Cathode / electrolysis?

Just for clarity, fixed it for ya. Baking soda won't do much in the electrolysis department.

[Bob Holmes]

Just thinking out of my butt here, don't flame my pathetic attempt at mr. science...

Beags: I've got a Masters Degree in Sphincter Engineering, also. So you're among people of a like mind...

[1931s/x]

i build all of my own exhausts, and have never found the need to remove the coating before welding.