I'm not Lichen This Too Much

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Forum topic by HorizontalMike posted 02-18-2020 08:42 PM 996 views 0 times favorited 20 replies Add to Favorites Watch
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7928 posts in 4074 days

02-18-2020 08:42 PM

Topic tags/keywords: lichen wrought iron bench outdoor furniture

I have been busy cutting, drilling, and varnishing many cedar boards for some old Wrought Iron and wood outside benches. Got the wood all spar varnished/finished but have run into a problem with the Wrought Iron. It has lived outdoors in Texas for 10-15yr. It was originally BLACK, but as you can see, it is now green lichen covered and refuses to come off, even with a steel wire brush! I swear this is not like removing paint and probably more like an anodized coating, but harder.

There is nothing remaining that is loose, as these have been washed and brushed thoroughly. So far no amount of elbow grease, mineral spirits, ETOH, has worked. I have had a “bit” of success with acetone, however I estimate that I would have to use 2-3gal. of acetone and STILL a boatload of elbow grease.


1. Do any of you have experience removing lichen from wrought iron?

2. Is there a point where I can ignore the remaining lichen and paint over it?

3. I am trying to NOT have to use harsh chemicals/solvents and such. Would adding some KILZ to the prime coat be required, or am I over thinking this?

-- HorizontalMike -- "Woodpeckers understand..."

20 replies so far

View SMP's profile


4430 posts in 1065 days

#1 posted 02-18-2020 08:50 PM

If I remember correctly some types of lichen use calcium, similar to calcareous algae in saltwater. You could try some CLR in a test location.

View LeeRoyMan's profile


1945 posts in 887 days

#2 posted 02-18-2020 09:16 PM

I was originally BLACK, but as you can see,

- HorizontalMike

Yeah, you have to be careful with that Acetone, it’s pretty strong stuff! LOL

Have you thought about sandblasting.
I have a small gun, (tube that goes into the material), that hooks up to the air compressor, perfect for jobs like this.

Here is a harbor freight gem

View Don W's profile (online now)

Don W

20121 posts in 3727 days

#3 posted 02-18-2020 09:31 PM

try some vinegar. If it works, and you use it, make sure you neutralize it with baking soda and wash it well after.

-- - Collecting is an investment in the past, and the future.

View Joe Lyddon's profile

Joe Lyddon

10963 posts in 5212 days

#4 posted 02-18-2020 09:43 PM

I like all of the above ways to try…

In addition, it might help to also try Evapo-Rust... Although you don’t have a RUST problem, this stuff really CLEANS stuff up GOOD!

If it doesn’t work, you can still use it for other Rust problems you may have… Not all would be lost.

Looks like COOL metal work!

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:

View CaptainKlutz's profile


4674 posts in 2654 days

#5 posted 02-18-2020 10:00 PM

That color looks like standard cadmium (fake gold) metal plating to me?

If plating is not flaking off:
Clean it with little diluted vinegar (or commercial metal prep) to clean/etch metal pores, and then prime/paint as you wish. In metal world, cad plating is often used as barrier to prevent rusting and provide excellent paint adhesion!

As always, test before committing entire project.

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View corelz125's profile


3287 posts in 2136 days

#6 posted 02-18-2020 11:59 PM

Have you tried one of these on a 4” grinder? Lean into the grinder with one of those things on and they removal all types of material.

View Kelly's profile


3644 posts in 4104 days

#7 posted 02-18-2020 11:59 PM

I have to wonder:

“Hydrochloric (muriatic) acid is an excellent and effective way to clean rusty steel. However, it can also cause you great harm if it is not used properly. Be sure to use all safety precautions and work in a ventilated area to protect yourself from fumes. If necessary, consult an expert for further guidance.

Don all necessary safety gear, including goggles, thick clothing, work boots and filtration mask, which will protect you from vapors from the reaction of rust and muriatic acid. Find a well-ventilated area to work in; ideally, this will outdoors in an area with good air circulation.”

View Kelly's profile


3644 posts in 4104 days

#8 posted 02-19-2020 12:06 AM

Off on the side, is there any chance this was done to imitate patinad copper, then got painted?

View Jim Finn's profile

Jim Finn

2889 posts in 4082 days

#9 posted 02-19-2020 12:13 AM

I like what I see. Leave it! Painting it will degrade the look of it. Clear finish maybe. But that is just my opinion, I may be RIGHT!

-- No PHD just a DD214 Lubbock Texas

View a1Jim's profile


118163 posts in 4737 days

#10 posted 02-19-2020 02:42 AM

View Phil32's profile


1496 posts in 1063 days

#11 posted 02-19-2020 02:49 AM

I agree the Kelly. This looks like the verde gris finish often given to bronze. Someone maybe didn’t like it and painted black over it.

-- Phil Allin - There are woodworkers and people who collect woodworking tools. The woodworkers have a chair to sit on that they made.

View HorizontalMike's profile


7928 posts in 4074 days

#12 posted 02-19-2020 12:25 PM

Hi Mike
If you can get it blasted with walnut shells that should do it .
- a1Jim

Thank you Jim and LeeRoyMan, I was/am actually considering just that. I remember back on the SW-Forums, I had suggested just that, though with a cheap $5.00 DIY approach. I already have a 33gal adjustable compressed air setup. And I also have a stock of walnut and corn husks that I tumble my brass in. Only lacking the long metal tube, but at $5 all I need now… patience and order it… ;-)

-- HorizontalMike -- "Woodpeckers understand..."

View Snipes's profile


459 posts in 3404 days

#13 posted 02-19-2020 05:00 PM

I like the Green..

-- if it is to be it is up to me

View Phil32's profile


1496 posts in 1063 days

#14 posted 02-19-2020 05:34 PM

Here’s a description from Wikipedia -

Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over time. It is usually a basic copper carbonate, but near the sea will be a basic copper chloride. If acetic acid is present at the time of weathering, it may consist of copper(II) acetate.

It may not come off per your plan

-- Phil Allin - There are woodworkers and people who collect woodworking tools. The woodworkers have a chair to sit on that they made.

View HorizontalMike's profile


7928 posts in 4074 days

#15 posted 02-19-2020 05:59 PM

Well, would you/anyone think that these relatively cheap big box store benches have copper in their wrought iron bases? These were commercial benches from China, so who knows…

Or is what I have actually “cast” iron with copper as an alloying element?


Alloying elements
Cast iron’s properties are changed by adding various alloying elements, or alloyants. Next to carbon, silicon is the most important alloyant because it forces carbon out of solution. A low percentage of silicon allows carbon to remain in solution forming iron carbide and the production of white cast iron. A high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, manganese, chromium, molybdenum, titanium and vanadium counteracts silicon, promotes the retention of carbon, and the formation of those carbides. Nickel and copper increase strength, and machinability, but do not change the amount of graphite formed.

-- HorizontalMike -- "Woodpeckers understand..."

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