REPAIRING PLATING ROOM FLOORS

by Walter Lee Sheppard, Jr.

GGRM Inc., Havertown, Pa

Every plater is faced at one time or another with the problem of repairing or replacing thefloor in his or her plating room. The plater wants to do it as quickly as possible so as to get backinto production with the least downtime. yet to make a repair that will last This is particularlyimportant where there is automatic machinery-where plating racks are lowered. timed. andraised in an automatic cycle. anddeterioration of the floor can makea tank tilt out of alignmentand cause the rack to hang up on a tank wall.

In the past. small plating shops have made do at the stan with an existing floor in aconverted residential building where the floor is often of wood . Consider the problem that mayexist with the heavy standing load of liquid-filled tankage on floors that were designed tosupport people and their furniture . The first thing 10 do is to check the beams and supports tobe certain that their design is adequate and condit ion sound . A local contractor or engineerfriend can do this for you at minimum expense and it is of key importance to your success. Theengineer should consider inadequate any floor that will deflect visibly under the load that youexpect to place on it It is acceptable to feel movement as long as you cannot see it

Ifthe tanks are placed so that liquid dragout on the work or racks drips on the wood floor.no amount of washdown can save the floor from serious damage. If you have tried operatingwithout a protective surfacing over your floors. you have already discovered this. and you mayhave also discovered damage on the floor below caused by leaking from the operations.

The best protection. if your floor supports are strong enough. is to cast a 4-in. reinforcedconcrete slab on top of the existing floor. andapply a preferably thin (\ I/4-in.)acid-brick floorover the concrete. employing a hot asphalt membrane between the concrete and the brick. (Seearticle on Acid Resistant Floor Construction elsewhere in this Gll idebook.)The second choiceis a I/4-in. trowelled epoxy floor surfacer over the concrete. Be careful to install a proper drainin the concrete and to slope the surface to it A polymer concrete may be an acceptablesubstitute for both the concrete and the topping.

If the existing floor is unable to support the weight of the concrete in addition to that ofthe loaded tanks. all is not lost There remains a compromise. which if properly installed andmaintained, can last for many years. Clean the old wood floor thoroughly. replacing anydamaged or badly worn timber. Then. bring in a large sander and run it over the old floor to geta completely uniform surface. Now nail down over the old wooden floor sheets of '1M'in. thickor thicker marine plywood, butting all the edges tightly and smoothly together. andcountersinking all nails. Over the marine plywood apply. as first choice. a hot asphaltmembrane and 21/4-in. (not thinner) acid-brick. Expansion joints should be placed at IS ftintervals or less.

If this is beyond the weight limitations. then the second choice is a I/ ....in. thick epoxysurfacer. If the epoxy is used. place expansion joints around the periphery of every sheet ofplywood. matching the expansion joints 10 the cracks between that sheet and the next Bothtypes of floors have served successfully for years over this type of substrate. provided that theyare properly cared for and maintained. This means repair as soon as a crack appears. Do notdelay.

If the floor under the duck boards is plain concrete. or concrete protected only by a paintcoating. andhas been subject to spills and drips for a long time. the damage will be extensiveand will COver the entire working area. Under such circumstances. there may be such structuraldamage to the building as to make repair a waste of money. or so much plating waste may havepenetrated the soil under the floor as to cause problems with the EPA. In either case.excavation of the diseased concrete and of all badly contaminated soil must be accomplishedbefore the work area can be rehabilitated.

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Fresh concrete. properly designed and reinforced. is then installed. with the reinforcingtied in solidly to the reinforcing in the walls and elsewhere in the building . Before consideringmeasures to protect the new concrete from experiencing a repetition of this damage. theconcrete must be permitted to cure. freeof traffic, or the spillage of any corrosives. The use oftype 111 Portland cement in the mix will provide acceptable strength in four days. However.faster strength development and readiness to accept the corrosion resistant surfacing can bemore quickly supplied by the useof a super plasticizer in the concrete. while simultaneouslyretaining "slump" at a maximum of 4 in. With the appropriate amount of super plasticizeradded and using type I Portland, full strength (not just a workable percentage) will bedeveloped in 72 hours. and with a reduction of 30-32% of water demand. In 28 days. theconcrete will develop a 190% design strength and the low absorption of 5--6% as comparedwith "normal" concrete absorption of approximately 20%.

If this route is followed, the new concrete surface should be decreased by the thickness ofthe surface protection planned. With an acid brick, this would be 25/1 in. (including II. in. foran asphalt membrane plus 21/. -thick shale brick with a I/R-in. bed joint of mortar), Lesserthicknesses of brick may be used if desired, but labor and material costs will not be muchdifferent if II/R-in. red shale splits or ll/.-in. pavers are used. and the delivery time may belonger. Do not go under I in. thickness and do not usequarry tile. With a polymer concrete. thesame general construction may be accomplished.

If a It..-in. epoxy monolithic topping is used, the change in elevation is slight. but theIt4-in. slope to the foot required in this case may affect the location of services if the originalfloor is dead flat.

If the floor of the shop is new. or if the shop has only been operating for a short timewithout floor protection. it would be wise to arrange for floor protection at the earliest availabletime. closing off and working on each individual area in tum. If the work is to be done in thismanner. the least downtime will be experienced if castable floor surfaces 1- to 2-in. thick areplanned to cover the existing floor. This will mean elevating all services. electrical andplumbing. in each area. That work may be done at the same time the floor contractor is cleaningthe surface of the floor that is to be elevated, before applying the new surfacing.

Though an acid brick floor properly selected and installed is the best protection you cangel, it would require at ~east double ~e downtime of the monolithic surfacing and wouldnecessitate further elevatIon of the services.

Inasmuch as no castable monolithic or polymer concrete can tolerate exposure to the fullrange of corrosives in a plat~g shop. it IS important to plan to segregate your operations andassign specific areas for specific exposures. ~1.1 ch~me work. where there is a possibility ofchromic acid spillage, ~d all a:eas where ~1b1C acid over 5% concentration may be spilled.should be grouped and. If possible, done SImultaneously. A castable polyester or vinyl estermortar with acid brick, or a polymer concrete made from these same resins. is the type ofmaterial indicated in such a case.

In areas where any acids other than hydrofluoric are used and/or where caustics may bespilled, a furan concrete may be selected. In areas where spills may consist of strong bleach.weak acids other than hydrofluoric. mixed perhaps with any combination of caustics. epoxyconcretes areindicated.

Where hydrofluoric acid or strong alkali exposure areanticipated. the same resins may beused as just mentioned. but the fil!er m~st be.carbon•.such as crushed anthracite .

Recently. there has been an intenslfied interest In the use of sulfur concretes in platingshOps. The plater should be warned..however, that copper and beryllium salts react very slowly

er a period of a year or more With sulfur concrete and sulfur cements to form expanding;'owth salts. a reaction that can eventually destroy the floor. In such areas, brick mortared with

lfur cement or a sulfur concrete obviously should not be used. It should also be noted that:~Ifur mortars and concretes can be injured by exposures for any extended periods to live

steam. I . h d h d . . iedA great many sa es puc es an muc a vernsmg accompam by case histories haveappeared in technical literature over the past decade. pushing the use of silicate castables as

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floors in chemical areas. They often claim satisfactory operation in areas of exposure toeverything except hydrofluoric acid and acid fluorides, within a pH range 0-9, sometimeseven0-12

The plater should receive these claims with caution . Although it is absolutely true thatsilicate castables and silicate concretes have outstanding resistance to all acids excepthydrofluoric (and acid fluorides), when subjected to alkalis in a continuous exposure they willbe quickly damaged and, in a short time. destroyed. Silicates resist organic materials with pHranges as high as 9, and for a short period of time the bases of weak alkali metals. Even verydilute solutions of hydroxides of the strong alkali metals (sodium, potassium. and so on) attackthem very rapidly . Continued exposure to live steam and to running hot neutral or alkalinewater will wash them out.

Further, silicate castables (or silicate concretes) have far higher fluid absorption thanother polymer type concretes. To be used satisfactorily in plating service. they should only beemployed over positive liquid seal membrane. Without the membrane. liquids standing onthem or passing over them will eventually penetrate to the substrate below. and although theymay not damage the silicate castable, the penetrating materials still have the power to damagethe substrate. With the limitations just stated, silicate castables may be considered for use in afew specific areas.

Note that all polymer concretes are subject to hairline cracking over long periods of time.If a crack should occur it must be repaired promptly if the floor is to survive.

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