The International Cessna^® 170 Association

The fuselage walls aft of the baggage compartment of my '52 170B are coated with a black material that resembles automobile undercoating. Did Cessna apply this and if so, what is it? What is its purpose? Does it protect the aluminum?

My 52 has the same. I was told it was done as a sound deadening attempt. I guess it could help with oil canning too.

Thanks much for the quick reply

My 52 170b has black crap in tailcone also. Does not appear professionally done. My mech figures for sound deadening also.

Yes, it was intended to reduce “oil canning” in large flat areas and always has the appearance a child did it.

And according to Del Lehmann at Mountain Airframe in Mena, the black stuff is insoluble in just about everything. He tried every solvent he had and was not able to dissolve it on my plane. We finally gave up and primered-over it since the little bit they mechanically removed had no corrosion underneath it.

It's also a good indicator if any sheet metal has been replaced or if it's original.

MEK (alot of it) takes it off but its not worth the effort. And Yes, like Richard said, I thought it looked bad (and does) but zero corrosion underneath it.

It's about 200 hours sweating in a respirator to get it all off from tip to tail. Mine had some minor surface corrosion below it occasionally.

Vertical wrote:It's about 200 hours sweating in a respirator to get it all off from tip to tail. Mine had some minor surface corrosion below it occasionally.

OK, I'll ask, how did you do it?

Blood, sweat, tears and marital strife.
Also:
Plastic razor blades from amazon
Red scotch bite
Klean-Strip gel "Aircraft" paint remover from the auto parts store (chloride free).
3m General Purpose Adhesive Remover
Dumond Smart Strip Pro paint remover. Smear on, and put cellophane plastic over for a couple hours.

Lol....and I thought this was something they did to mine while it was up in Alaska for 30 years... my tail from the baggage compartment back has it, and the lower nose bowl & cowl doors... It looks to me like a product we used to use in Michigan back in the 70's called Zeebart, real waxy. I found a heat gun & plastic scraper sort of effective for removing the areas coated on the cowling when I installed the Davis cowl latch STC.

I’m curious as to Why an owner would wish to remove a protective, costly treatment Cessna considered beneficial/worthwhile.

Probably curiosity/worry about condition of underlying aluminum, now 70 years old. Also appearance. That would be my guess.

It's faster and cheaper to replace the skin(s) than to remove the goo. I'm pretty sure MIL-H-5606 dissolves it, but makes a bigger mess and apparently takes a few decades.

My 1950 170A (now sold) was previously in BC on floats and we thought that coating in aft fuselage might be some kind of seaplane treatment, maybe moisture barrier. Never tried to remove it. Any concerns with 5606 on aluminum?