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Alodine 1200 - Chromate Conv Process


What is that golden-brown color on the back of my sign?

Steel, iron and most other metals, when in contact with water, will oxidize and develop RUST; the reddish-brown color we’re all familiar with. Over time, it can cause severe damage, which is why traffic signs have not been made out of steel since the 1950's.

ALUMINUM, however, can NOT develop “Rust”, but like all metals (and under the right circumstances), aluminum will oxidize. When oxidization on aluminum occurs, ALUMINUM OXIDE (a.k.a. “White Rust”) will develop.

Contrary to popular opinion, aluminum can be more prone to oxidation that steel or iron!

But, fortunately, under “normal” conditions, aluminum oxide will NOT occur on exposed surfaces of a reflective aluminum sign; rain and water will simply drain off a sign mounted on a sign post and evaporate without having the time to oxidize.

However… if the sign is

  • stored flat or against another sign
  • water is allowed to “pool”
  • mounted against a wall or other surface
  • in very wet or humid climates

aluminum oxide can develop over time.

Aluminum oxide that forms on the BACK of a sign is unsightly, but no other serious detrimental effect occurs.  

However... moisture from rain and humidity can actually work its way UNDER the reflective sheeting on the FRONT of a sign.  If / when this occurs, the reflective sheeting can crack, "bubble up" and become detached from the oxidized aluminum sign blank it is attached to, resulting in the need to replace the entire sign prematurely.

Fortunately, there is a process that can minimize the chances of aluminum oxide from developing.

We only purchase aluminum sign blanks that have been treated with Alodine 1200™; the best Chromate Conversion Process to help prevent aluminum oxide from forming of the front, back and edges of an aluminum sign blank.

Although most sign shops do NOT purchase sign blanks treated with a Chromate Conversion Process, we believe this modest additional expense is critical to make the best, most durable signs available.

Sometimes you can see it... sometimes you can't.

  • Most of the time the Alodine coating applied at the aluminum mill is ‘all-but-invisible’, but occasionally “streaks”, "blotches" or an “overall” golden-brown color from the process is visible on the back of the signs.
  • This is normal, is only “cosmetic” in nature, and will not adversely affect the sign.
  • In other words, if you see any traces of this ‘golden-brown’ color on the back of your sign, rest assured it is “a very good thing” and will insure that you have purchased the best, most durable and “white rust resistant’ sign available.
  • If, however, no ‘golden-brown’ color is visible, rest assured that the Alodine is there; the aluminum mill simply applied a perfect, even and “invisible” coating and/or clear Alodine vs. brown Alodine was applied at the aluminum mill.

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