Posted by Phil S on 10/04/2022 23:13:28:
About fourteen months ago I purchased a new 6 inch M&W square to replace the thirty year old, worn out one that hangs over the bench. For a reason now forgotten I did not do the exchange, but put it back in the box and put the box on the shelf. In haste I failed to fully enclose the square inside the brown paper liner. The photo shows deep pitting, the result of letting the cardboard lid touch the metal … I note that the brown liner paper was not the usual oiled type but has a plastic layer fused to the outside. If anyone out there has M&W items in similar packaging they might wish to review the arrangement.
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Bad luck! I think M&W's packaging is mostly innocent though.
The filmed anti-corrosion paper keeps water out, whilst the waxy side is in contact with the metal. The cardboard box reduces the amount of moist air that can get to the metal. All good, but the wrapping has to be in place and the cardboard box sealed: sometimes new tools are taped shut or come in plastic.
The damage was done by condensation, which occurs even in dry garages. UK air is often wet, and we make it worse in workshops by breathing. Condensation occurs whenever warm moist air comes into contact with cold metal. It's common because workshop temperatures rise naturally in the day and fall overnight, whenever work is done, and especially if the workshop is heated to work in it.
I think what happened to the square is that air was able to flow in and out of the box, where moisture condensed on the exposed metal and soaked into the the cardboard. Ironically the metal, box and temperature changes acted as a pump, capturing water rather than keeping out. Any salts in the cardboard would increase rusting, so the square was stored in a damp box, probably slightly acid.
General cures for condensation:
- Remove water. Fix leaks, dehumidify, ventilate, store in sealed boxes etc.
- Reduce temperature swings. Ideally everything in the workshop should stay at the same temperature whatever happens. Cool is better than hot, because the speed of a chemical reaction like rusting rises with temperature.
Hard to do, and potentially expensive, so palliatives:
- Maintenance waterproofing – oil, waxes, paint, galvanising, anti-corrosion paper, tools in cupboards, boxes and plastic bags etc etc. Note it's hard to maintain a completely effective air seal .
- Water reduction – no naked flames, drying washing, open water tanks, or damp floors and walls, blowing moist air out with a fan, dehumidifier, silica-gel etc,
- Reduce temperature swings with insulation, ideally the whole workshop, but blanketing helps too. Make sure blankets don't trap water! Attaching a small electric black heater to a machine tool will reduce condensation by keeping the metal closer to air temperature.
Condensation is difficult to deal with because the only guaranteed answer is an expensive environmental control system – 24×7 air-conditioning with temperature control. Lesser measures depend on local circumstances, which is why what I do successfully in my workshop may not work for you and vice versa.
Before reusing the M&W box, make sure it's dried out!
Dave