Corrosion on Malleable Iron Pipe Fittings

[Kaizer Soze]

Hi.

We have a consignment of Malleable Iron Pipe Fittings that has rusted due to water and weather damages over a period of time. Attaching photographs for your reference:

What would be the most ideal solution to get rid of all the rust and restore all these fittings back for commercial use.

One method was to use WD40 to spray on each fitting and have it brushed, sanded and wiped clean. However, this is an extremely slow process.

Any suggestions and what would be the optimum solution / solutions?

Thank you.

 

[weldstan]

There are plenty of light acids that will remove the rust. Phosphoric and citric come to mind. Low concentration stronger acids will also rapidly remove rust.

 

[TugboatEng]

The rust is light. A dip in any acid will work. I do recommend a dip in water and sodium nitrite solution at 3000-6000 ppm after the acid wash to neutralize the acid and prevent flash rusting as the fittings dry.

 

[moltenmetal]

Agree with the rest- a light acid pickle followed by rinsing, but I'd suggest phosphating and applying a little light oil as a final step before they go back on a storeroom shelf.

 

[mrfailure]

Of course, make sure after rust removal that your fitting still meet dimensional requirements for the application.

 

[moltenmetal]

The rust is superficial so no worries there.

 

[GarryB1957]

Not being funny, but a quick cheep method is, drop them in a bucket of Coca Cola (genuine coke) leave overnight rinse and dry

 

[moltenmetal]

@GarryB1957 indeed, Coca Cola is a fairly cheap source of dilute phosphoric acid solution.

 

[Compositepro]

There is 17 mg of phosphoric acid in 100 ml of Coke, making it a poor source of acid. The carbonation is the bulk of the acidity.

 

[TugboatEng]

Concrete etching solution available at your local hardware store is the least expensive way to aquire phosphoric acid.

 

[Compositepro]

Concrete etching has traditionally used hydrochoric (muriatic) acid. Phosphoric is much more expensive. I researched The Home Depot etchant and found it is what is called urea monohydrochloride, which I had never heard of. It is a 1:1 mixture of urea and hydrochloric acid, which forms an organic salt. It appears to be a safer substitute for hydrochloric acid in consumer products, which is being pushed by USA and European government chemical safety agencies.

If I were cleaning rust from a ton pipe fittings I soak them in 5% hydrochloric acid until clean. The dilution slows the process and increases the liquid volume to allow full submergence of the fittings without wasting acid. The etching takes longer but that is good because it takes time to handle a ton of fittings. Rinse with hot water so the fittings dry quickly.

For a single item I have used concentrated acid and the surface is clean in a couple minutes.