I don’t like ASTM B117 Salt Spray Tests

For one thing, they are only loosely related to the real world.  No rainstorm (especially no rainstorm carrying heavy salt concentrations) continues unstopped for hundreds of hours.  The real world works more like cycle testing: stop the weather, let it dry, hit it again. And the correlation to the real world durability is never precise: neither test actually achieves one-to-one predictability to an exact month.

Okay, they have a relative value.  I guess if you subject two materials to the same stress at the same time the best you can say is that one is better (even much better) at withstanding that particular stress condition. If you cut or perforate or scribe a couple of  pieces of galvanized metal, and one rusts on the cut edge, one rusts on the edge of the perforation, one rusts on the scratch—and the others (say, the ones with InterCoat®ChemGuard) do not, the best you can say is on all those tests, it dramatically outperforms the others.

If you place panels outside in Gary, Indiana for three years, or bury panels in the ground in Gary, Indiana, (see pictures here) and there is no corrosion, then the best you can say is that in that location the InterCoat®ChemGuard is superior to anything ever seen before. But that does not say how they may perform in another location.

If you weld galvanized metal or cold reduce it to 50% and the embedded, covalently bonded InterCoat®ChemGuard and its correlative corrosion protection does not leave the zinc, does not become somehow “unbonded” or unattached, the best you can say is that it seems to be a molecular bond under those circumstances.

Well, even on a relative basis, it is interesting and chin-scratching to see a substantial difference in performance. It makes one curious.  If a piece of HDG G235 is consistently full of red rust after many tests (see graph below) and others with InterCoat®ChemGuard are placed in the same test for twice as long with no rust, it makes you wonder.  Seems clear that, however “good” or bad the test is, something’s obviously going on.

 

  • HDG G235 + Hexavalent Chemtreat
  • HDG G165 + Hexavalent Chemtreat
  • HDG G90 + Hexavalent Chemtreat
  • HDG G60 + Hexavalent Chemtreat
  • HDG G30 + Intercoat ChemGuard